Collie Color Schemes

Dealing with the various colors of collies on a scientific basis, one gains highly interesting insights.


Sable & Tricolor

Let us start with the fact that from a scientific perspective only two colors exist for the collie, Sable and Tricolor. Sable is a brown shade, ranging from light gold to dark mahogany, depending on the shading.


 Dark Sable / White:

("Cook's Nevada" by Marion Henkel)


Tricolor is equivalent to the black shade, sporadically framed by red brown tan markings, especially on the cheeks, as a small patch above each eye, sometimes on the chest, on the tail and most commonly on parts of the legs.



("Eu.Sg. Overland Opening Night BOB, BISS" by Heike Ankele)


The brown color of the Sable and the black color of the Tricolor stretches from the nose, around the eyes and over the forehead and ears (mostly interrupted by the white collar), over the complete back to the tail (exact the tip) and the upper part of the legs, sometimes far down. This brown and black color is determined by eumelanin, whereas the tan markings are determined by pheomelanin. Color defining cells called melanocytes provide their color (contained in so-called melanosomes) to the hair follicles of the growing fur. These cells originally derive from the neural crest. During the embryonic phase the progenitor cells (melanoblasts) wander into the skin (epidermis). It is interesting that these cells do not only exist in the skin, but as well e.g. in the oral mucosa, even in the heart and in one of the cerebral membranes. Additionally, they also exist in the inner ear and in the iris of the eye.



("Daya von Spirit of the Scottish Highlands" by Martina Becker)


How come that some collies are Sable and others Tricolor? From biology classes we know that each cell as well as each egg cell contains all necessary genetic information to be able to form a new organism once both cells have merged (fertilization). The genetic information differs in each egg and sperm, depending on the possible genes of the parents that are available. Which particular egg and sperm cell merge is coincidence. This explains why each individual has a very distinct appearance. It is well known that each ovum and each spermatozoon contains only half of the set of chromosomes of genetic information (DNA). Only after fertilization, when both sets have attached correctly to each other, new life can be formed. Each part of the chromosome - called gene – comprises of two alleles, one from the mother and one from the father.



Pure Sables e.g. have received a Sable allele (Ay) from each parent. If both alleles are identical it is also called homozygous Sable. It does exist in various shades, from light gold (Gold Sable) to intense brown. These collies can only pass on Sable alleles. They never can have Tricolor offsprings as they don’t possess Tricolor alleles (at), in contrary to Dark Sables. But if a Sable allele should encounter a Tricolor allele this results in a Dark Sable to be born (see below). Only genetically confirmed Pure Sables are listed as such, otherwise the name Sable remains.


Pure Sable  (Gold Sable) / White:

("Rose River's A Touch of Magic" by Beate & Bernd Rosenbach)


 Pure Sable / White 

("Gaylord vom Zauberwald" by Christina Meier)



Parents:                       Pure Sable
Pure Sable                 100% Pure Sable
Dark Sable   50% Pure Sable  + 50% Dark Sable
Tricolor                 100% Dark Sable




Tricolore haben von jedem Elternteil ein Tricolor-Allel erhalten, sind also homozygote Tricolore. Sie sollen idealerweise ein kräftiges Schwarz (Lackschwarz) haben, ohne jeglichen Rotstich. Hinzu kommen die oben beschriebenen Tan-Abzeichen. Sie können nur Tricolor-Allele weitervererben. Trifft ein solches Tricolor-Allel allerdings auf ein Sable-Allel, dann wird ein Dark Sable geboren, da Sable die Farbe Tricolor unterdrückt (siehe unter Dark Sable). Tricolore können nur dann geboren werden, wenn ein Tricolor-Allel auf ein anderes Tricolor-Allel trifft (durch den rezessiven Erbgang, siehe auch unter Dark Sable) . Dabei ist egal ob es von einem weiteren Tricolor stammt oder von einem Dark Sable.



("Asana Zafu du Finfond" by Catherine Brisedou)



Parents:                           Tricolor
Pure Sable                    100% Dark Sable
Dark Sable         50% Dark Sable +   50% Tricolor
Tricolor                     100% Tricolor


Dark Sable:


But what happens if a Sable allele encounters a Tricolor allele? Today it is well known that Sable "dominates" over Tricolor or to phrase it the other way round Tricolor is "suppressed" by Sable, because the puppy deriving from this mating is Sable colored. Scientifically phrased, Sable possesses a dominant and Tricolor a recessive inheritance. If a sable and a tricolor allele meet, this is also referred as incomplete penetrance, both colors prevail, the brown color well visible and the black color only indicated. The new-born puppies are of comparably dark color but become lighter and lighter in the following weeks so that they resemble Pure Sables. But with increasing age, by most of the Collies, the Tricolor allele also becomes prevalent to a certain degree. In other words, the black color from the melanosomes finds its way into the hair follicles of the growing fur. Because of this, the brown color becomes increasingly darker especially on the back, even to the extent of dark mahogany. Some hair appears to be of intense black. Most of the times these dogs at birth had dark hair at the root of the tail and later on also at the longer lateral headhair where the neck starts. One can also say that the inheritance of Sable is incompletely dominant and the inheritance of Tricolor is incompletely recessive. Collies with a Sable allele and a Tricolor allele or so to speak with a Sable-Tricolor gene are also called Tricolor-factored Sable, better known as Dark Sable (Ay/at). Because of the difference of the two alleles (Sable and Tricolor) it is also called heterozygous Sable. These dogs can pass on Sable alleles (50%) as well as Tricolor alleles (also 50%). Succeeding inheritance is described above (see Sable and Tricolor).


Dark Sable / White:

("GCH Rose River's Blues of Paradise" by Beate & Bernd Rosenbach)


The distinction between darker Pure Sables and comparably light Dark Sables can often only be ensured through genetic testing. Or by looking at the offspring if a Dark Sable or a Tricolor is chosen as mating partner, because only if the original dog is a Dark Sable can Tricolors be born. However, this approach is rather unreliable. A supposed Pure Sable recently sired 2 Tricolor puppies after having sired 30 puppies before. This happened all of a sudden although through the selected mating partners he actually should have sired Tricolor puppies before. This emphasizes the theory of inheritance. Mother Nature is always good for surprises when genes encounter each other and this is indicated here as well. In this context, it should also be noted that only secured Dark Sable are named as such, otherwise they are listed as Sable.


 Dark Sable / White:

("Lucky Stars Asuka" von Claudia Gebhard)



Parents:                            Dark Sable
Pure Sable           50% Pure Sable +   50% Dark Sable
Dark Sable25% Pure Sable +   50% Dark Sable + 25% Tricolor
Tricolor             50% Dark Sable +   50% Tricolor



There is now a much more detailed breakdown of the coloring alleles of the primary colors Sable up to the Tricolor on the A locus:



There are two variants of White by Collies, on the one hand as markings (like white collar, breast, belly, lower parts of the legs, paws, tip of the tail) and on the other hand as extensive White Patches. The latter ones are called White Collies or Color-Headed-White (CHW) because the head always has to be colored. Both variants of White are caused by different genes. These are summarized under the term MITF. As described above, the coloring of the fur is caused by the release of brown or black color through melanocytes (coloring cells). The color (contained in melanosomes) is provided to the hair follicles and the growing fur incorporates the pigments. MITF genes prevent the absorption of pigments. In this sense, white is not a color but rather the absence of color, or better said the absence of pigments. MITF genes do not induce any other defects on the White Collies. This means it is completely irrelevant which MITF gene (Irish pattern or Piebald, see below) causes the apparently white areas. Or said in other words, White Collies are just as healthy as colored Collies that are only white at the markings!


White / Tricolor:

("Rose River's Konquest of Paradise" by Beate & Bernd Rosenbach)


White / Blue Merle:

("Rose River's Galactic Storm" by Tomoko Ferraino)


White Markings:


By Collies and many other Herding Dogs, the white markings are genetically fixed by two identical (homozygous) alleles called "Irish pattern". Through incomplete penetrance it can result in various characteristics (e.g. a particularly wide collar to an unclosed collar). But each collie possesses this gene by inheritance through the parents and passes on to the offspring accordingly. That is also the reason why the sable-colored Collies in America are not simply called as "Sabel," but as "Sable & White". "White" just meants the white markings. By Tricolors there is not this supplement. For the sake of completeness, I like to mention that "Sable Merles" (described below) are included by the "Sable & White" in America. They are not explicitly mentioned in the originaly breed standard. Therefore a dark brown eye color is preferred, even if brightness or blue colorations in Merles occur frequently. The same applies to the remaining little brown stains in adulthood in rare cases by Sable Merles, it is also not desirable. Many judges consider such color variations (especially as eye color, rarer than skin color), as a disturbance of the harmonious overall appearance.


Sable / White

("Heatherland's Royal Flush by Yvonne Kreft)



Parents:               White Markings
White Markings
          100% White Markings




White Collies appear to the observer as White Collies with a colored head and some colored "patches". But scientifically they are Sable or Tricolor Collies (by some exemplars with brightened colors to a Merle, see below), with an extensive white piebald. There where one can usually see brown fur by Sables (or Sable Merle, see below) or black fur by Tricolores (or Blue Merle, see below), can see now a widespread white, which reaches over the complete back part right all the way down to the extremities, except for a few spots (patches) in the original color (Sable or Tricolor). What happened? Similar to the Irish pattern gene that causes the white markings, here the so-called "Piebald gene" prevents the absorption of pigments into the impacted areas of the fur. Likewise incomplete penetrance can lead to diverse characteristics. The so-called "No Spots" just have a colored head and maybe a colored root of the tail, the rest of the dog is completely white. However, collies whose white spotting makes up around 80% are considered originally desirable. The remaining area is taken up by smaller areas in the original color, or better said some areas are excluded from the extensive white piebald. With such spots, pigmentation occurs in the original color of Sable or Tricolor (or their lightened colors, such as Sable Merle and Blue Merle, see below). When giving the exact name of the Collie, a slash is placed after the White and then the original color is added, such as White / Sable or White / Tricolor etc. Some also speak of factoring, for example a White / Tricolor is a White Tricolor-factored Xollie.


White / Dark Sable:

("Eu.Sg., CH Rose River's Cherished Hope" by Beate & Bernd Rosenbach)


White / Tricolor:

("Rose River's Glamours Pride" by Angelika Vossel)


Even so, the extensive white coloring depends on both Piebald alleles (this is also called White Factor) to be identical, i.e. homozygous. If it is only heterozygous, i.e. only one allele carries the White Piebald and the other does not, one speaks of so-called White Factored Collies. The color of these Collies is normal Sable (or Sable Merle) or Tricolor (or Blue Merle), but they often have enlarging white areas next to the markings, i.e. the extremities are often not only white on the paws, but the white is often drawn up to the knees, sometimes furthermore, especially on the inner thighs and along the belly. The White Factor has no direct influence on the collar size. But the collar often appears to be bigger due to additional white areas on the chest and belly. Because of the incomplete penetrance here, a less pronounced White Factor can sometimes only be assumed, but cannot be guaranteed, unless one parent is a White Collie, because then every offspring will have the white factor. On the other side, there are also Collies, nobody would assume that they have a White Factor from the appearance (phenotype), but they still have it. So there can be sometimes surprises by matings. Because White Factored Collies passes on the white-factor with a probability of 50%. If it meets another White-Factor, the puppy will be a White Collie. If it does not meet another White Factor, the puppy will only be White Factored. White Collies passes on the white-factor at a 100% with the same consequences as if encountered another White Factored. White is inherited completely independently of Sable and Tricolor (as well as Sable Merle and Blue Merle), similar to Merle (see below). If the White Factor is known, this is placed with a slash after the original color, such as e.g. Dark Sable / White.


 Dark Sable / White:


Piebald is not genetically fixated in contrast to Irish pattern. It is highly undesired according to the British breeding standards and White Collies – at least in Germany – do not get an approval for breeding. Breeders specifically have to take care not to mate white-factored dogs with one another. This even goes as far as to the fact that White Factored Collies are even not desired. In America are White Collie a normal and desired color variant, even though it is less common than Sable and Tricolor. In Europe, White Collies are still mistaken as Double Merles (see below) which can arise out of the mating of two Merles. Reason for this is ignorance, sometimes combined with deliberate misinformation. Depending from the Allele Variante, they can have too extensive white areas, so that by most of them also their heads are completely or partially white. This may be combined with hearing and vision disabilities right up to deafness and blindness. Further details see below. White Collies always have a colored head and they are completely healthy! To stay sure, one should ensure that dogs with very large blazes are only bred with those without blazes. Split faces, where one half is white, are not desirable.


White / Dark Sable:

("Rose River's Catch the Wind" - photo Beate Rosenbach)




Parents:                                                 White
White                                            100% White
Colored with white-factor
                            50% White  +  50% Colored with white-factor
Colored (no white-factor)                                     100% Colored with white-factor



Parents:                                        Colored with white-factor
White                          50% White  +  50% Colored with white-factor
Colored with white-factor
    25% White +  50% Colored with white-factor + 25% Colored (no white-factor)
Colored (no white-factor)                 50% Colored with white-factor  +   50% Colored (no white-factor)



Parents:                                       Colored no white-factor
White                                    100% Farbig with white-factor
Colored with white-factor
                 50% Colored with white-factor +  50% Colored (no white-factor)
Colored (no white-factor)                                   100% Farbig (no white-factor)




(Classic) Merle (m/M)


Merles, also called Classic Merles to better distinguish them from the other variants, are well-known to most people. The two colors Sable and Tricolor are not only available in the usual strong version, but also in a brighter form, some with a kind of patterns. Such color effects are caused by a so-called "lightening gene", known to many as "Merle" (m/M). So Merle is not an independent color, but rather just a kind of brightening. On the contrary, it prevents extensive pigmentation, i.e. coloring of the fur, and also causes a kind of pattern. Usually only the colors caused by Eumelanin are affected. By Classic Merles (m/M), the black of the Tricolor, apart from a few small dark spots (large spots are undesirable), lightens to a light silver-blue color (dark steel gray is undesirable), while the red-brown Tan Markings (Pheomelanin) normally remain completely unaffected. Such collies are called “Blue Merles”. In a Sable, the brown (Eumelanin) is also lighter and they are called “Sable Merles”. The Merle gene is inherited intermediately, or more precisely, incompletely dominant. In other words, the affected animals are not completely silver-blue or light brown, but they still have spots of the original color that remain. In the case of the Blue Merle, you can still see black spots in the silver-blue fur, which it retains throughout its life. It's different to the Sable Merles, where you can often only see the spots on very young puppies. In most cases, the spots later will disappear again, so that often can often no longer easily distinguish an adult Sable Merle from a Sable without a Merle factor. Sable Merles derived from Pure Sables are often very similar to Gold Sables as adults, sometime a little faded. Sable Merles derived from Dark Sables can also be quite light, but they can also have a very strong, often almost reddish-brown color. Merle is inherited completely independently of Sable and Tricolor and also of White (and other factors such as D and E locus).


Blue Merle:

("Cara vom Heiligenstein" by  Martina Becker)


Blue Merle / White:

("Diva vom Zaubewald" by Andrea Schneider)


White / Sable Merle:

("Diva vom Zaubewald" by Andrea Schneider)


Sable Merle / White:

("Amor vom Zauberwald" by Lena Heime)


White / Blue Merle:

("Eloisa vom Zauberwald" by Brenda Hoogstede)


White / Sable Merle:

(photo: Andrea Schneider)


Blue Merle (m/M):

("Ju.CH, CH Lucky Stars Cold as Ice" by Sina & Christian Morgenstern)


Merle Grundvarianten (m/…)


Merle is a very old color variant and was mentioned in writing around 1800 and is probably much older, some suspect between 250 and 500 years. By herding dogs, Merle was and is still very popular with shepherds today. Not only because the color is different to the sheeps, but many are convinced that dogs of this color variant are particularly healthy, agile and willing to work! Even today, a particularly large number of Merles among the herding dog breeds can be found successfully in dog sports. In 2006, Dr. Leigh Anne Clark et al (USA) discovered that the gene section responsible for coloring (melanin storage), called the SILV gene, is supplemented by another piece of DNA by Merles, a so-called SINE insertion (short interpersed element ). This originally viral DNA, which is more common in various forms in humans and animals, can reproduce and insert itself. When reproducing the variant here, there may happen changes on the attached tail-like section A (A-tail). The shorter this section is, the less brightening effect it has, or even none at all. Merle free dogs have the m/m gene variant and there is no extension of the A-tail; the original 171 base pairs (bp) are retained. In 2018, Mary Langevin et al further broke down the length of the base pairs in relation to the different visible (phenotypic) formations, so that today there are 7 basic variants:


Length (bp)



Merle Patterns

Changing basic color

Changing eye color



Merle free (frei)




200 - 230


Cryptic Merle




231 - 246


Cryptic Merle +




247 - 254


Atypical Merle


slight brightening possible


255 - 264


Atypical Merle +


slight brightening


265 - 268


Merle (Classic)






269 - 280




Harlequin  Merle

Fawnequin Merle




Minimal Merle

(Phantom Merle)


smallest area


*in addition to the normal Merle pattern, there are often more or less large areas with pigment lightening up to white (regardless of the white factor) and large patches in the base color, in the case of the Harlequin in Tricolor and in the case of the Fawnequin in Sable (sometimes with color variations from light gold to reddish-brown and sometimes faded).

Regarding the eyes, it should be mentioned that there are also other causes of color change in the eyes. Typical for Merle variants (Ma, Ma+, M, Mh) is that lightening can occur from dark to amber in the Sable Merles & Fawnequins and Blue coloration in Blue Merles & Harlequins. For some the entire eye is affected, for others there are only slight spots of color. The eyes often have varying degrees of color up to no color at all. The extent and location of the discoloration are not genetically fixed, but are left to chance. The judges often prefer normal colored eyes for the desired expression.


Cryptic Merle (m/Mc, m/Mc+)


Cryptic Merles have the m/Mc or m/Mc+ gene variant. In terms of their phenotype, they look like normal Sables or Tricolors. Even if the gene section already shows an extension here, it is not long enough to produce pigment brightening anywhere. This is how the dogs grow up with their original intended coloring. There are reports here and there that the puppies may be a touch lighter at the ends of their hair shortly after birth, but this is no longer visible some time later. The genetic change is so small that, based on current knowledge, one could theoretically even breed Cryptic Merles with the m/Mc, m/Mc+ and m/Ma variants without puppies being born with health problems. The m/Mc variant (without a plus sign) even adds m/Ma+, m/M. In practice, however, it remains forbidden as long as the legislature fundamentally prohibits the mating of Merles, as it does not differentiate between the different basic types.


Cryptic (Dark) Sable Merle (m/Mc):

("Dt.CH Ohl-Family Magic of Lassie" by Lothar Köchling)


Important note: Earlier It was used to be mistakenly thought that the Cryptic Merles also included the Minimal Merles, as a kind of transition from Non Merle to the visible Merle variants, with their few small, often tiny Merle colored areas, which can easily be overlooked are then partially covered by white coloring (regardless of whether it is an Irish pattern, e.g. on the collar, legs, under the belly or due to the Piebald white spotting). Now with the new genetic tests (available since a relatively short time) and becoming possible to determin the exact allele name, it was discovered that they were completely wrong. Minimal Merles have the same genetic status as Harlequins or Fawnequins and can also produce them! Under no circumstances should Minimal Merles be bred with other Merle variants, as puppies with health problems can occur here! That's why owners of possible Cryptic Merle who do not have the clear result m/Mc or m/Mc+ (and of course also other Merle variants without precise knowledge of the alleles) should definitely feel encouraged to request the results or send in new samples, to make sure it really is a Cryptic Merle and not a Minimal Merle! In order to gain knowledge about such apparently invisible Merles, our breeding regulations have stipulated from the very founding of the club that they must be tested for Merle before mating.


Atypical Merle (m/Ma, m/Ma+)


Atypical Merles have the m/Ma or m/Ma+ gene variant. While by the m/Ma variant a slight brightening of the base color is possible at best, comes by the second variant m/Ma+ a slight Merle pattern usually through. The Tricolore's fur becomes silver-greyish, a faded merle pattern may or may not be visible. Sable can appear a little paler and no pattern will be visible here by adults. Atypical Merle can be seen as a kind of transitional form from Cryptic Merle to Classic Merle. The extended gene section is not as short as in the Cryptic Merle, but also not as long as in the Classic Merle. Similar to the Cryptic Merle, according to current knowledge, no damage to the health of the resulting offspring is to be expected from a theoretical mating of m/Ma with the variants m/Mc, m/Mc+ and m/Ma. With the m/Ma+ variant, mating with m/Mc would theoretically be possible. But in practice both remain prohibited, according to the requirements of the legislature.


Atypical Merle (m/Ma+ 236) / White :

("Int.CH Little Wolf vom Kaltwassertal" by Heike Ankele)


 Harlequin Merle / Fawnequin Merle (m/Mh)


At first glance, Harlequins resemble Classic Blue Merles to a greater or lesser extent depending on their characteristics, and Fawnequins resemble classic Sable Merles. Often the lightened areas (such as the silver-blue in the Blue Merle) appear even further brightened. In addition, the desired fine spotting in the base color (tricolor for blue merle and sable for sable merle) is usually less pronounced and is more likely found as patches. They are then also known as Herding Merles. Very large patches are also known as Tweed. Many are found on the edges and less within the brightened areas. This is also referred as a “loud Merle pattern”. By Sables, the color can deviate from the expected natural Sable color (sometimes faded), from a light gold tone to a reddish brown tone, the latter especially if a Tricolor Factor is present. What is particularly noticeable are the often new, more or less large white areas without pigmentation. They are usually the first reference to Harlequins or Fawnequins that particularly catches ones eye. They are not caused by a White Factor. The Tan Markings are usually normal. Harlequins/Fawnequins have the same genetic status as Minimal Merles (m/Mh), they can also emerge from them. These color variations are not to be confused with the Harlequin of Great Danes, which have an additional genetic change at the so-called H locus.


Harlequin (m/Mh):

("Brookwood's Spencer" by Marion Henkel)


Harlequin (m/Mh):


("Marjelchens Anna Lena - Taboo at Le Finfond"  by Catherine Brisedou)


In principle, Harlequins and Fawnequins, as well as the other Merle carrier variants (M/m...) are, according to current knowledge, completely normal, healthy dogs. According to this, the changes in Merle relate solely to pigment lightening or loss and not to other diseases or behavioral effects. Loss of pigment and the formation of white areas can only occur here at m/Mh. This also has no harmful effect. Only if the very unlikely case occurs that the inner ear or the inside of the eye also suffers a loss of pigment, is there a risk that puppies will be born with hearing or vision impairments of varying degrees of intensity. The affected ear is usually white or such an eye is surrounded by white fur. Since by Collies a colored head is required, the risk of health problems is very low, in contrast to completely white breeds (based on pigment loss, such as in White American Bulldogs). To ensure that it stays that way, Collies with m/Mh must not be bred to those that have an increased amount of White , such as a White Factor or a blaze that extends up to the forehead. In comparison, the risk of deaf Dalmatians being born is many times higher, which hardly seems to bother anyone, while a lot of nonsense is currently being spread about Merles out of ignorance. Here too, breeding with other carriers of the Merle factor is prohibited, same way as we do with other carriers in our club, such as MDR1, DM, PRA, GCS. A previous genetic test for everything helps to determine the exact status beforehand and to be able to choose the matingpartners so that no affected puppies can be born. In the many years of Collie breeding and research, I have never met a Collie with the genetic status m/Mh that has any hearing or vision limitations. If anyone ever finds such a case, please let me know so that I can correct myself here.


Fawnequin (m/Mh):


Minimal Merle (m/Mh)!!!


Minimal Merles, also called Phantom Merles, often look like normal Sables or Tricolors (phenotype) at first glance. If you look more closely, you will often find one or sometimes several small, sometimes even tiny areas, especially at the edge areas, where the dog has a normal Classic Merle color. Genotypically, as part of the new findings, people were very surprised when they found out, that the allele variant of the Minimal Merles (m/Mh) corresponds to that of the Harlequin / Fawnequin! Previously it was thought that they were assigned to the Cryptic Merles, as a transitional form to the Classic Merles, with the first possible visible Merle areas. Due to the actual allele variant, Minimal Merles are not allowed to be bred with other Merles like the Cryptic Merles, which also corresponds to the legal requirements.

The new findings about the genetic classification of Minimal Merles also show how important a genetic test for Merle is, even in dogs in which no Merle is visible, especially if Merle has already existed in the past. The owners of Minimal Merles are often not even aware that they have one. The Merle areas are not always actually visible. On the one hand, because they are so inconspicuously small or, in the case of long-haired dogs, they may be covered by overlapping fur, but also because it can be covered by other colors, especially White. For this the Collies don't have to have a White Factor; the appearance of the collar or white on the legs is enough. If the Merle area is sitting exactly at this point, which is often found in the edge areas, then it would be covered by White! The same would happen with the E-locus (for red-yellow coloring). It is extremely rare in Collies and is also undesirable. But when it occurs in dominant form, it covers all other colors, such as Sable & Tricolor, right down to the black nose, which then appears brightened. At first glance they often look like normal sable, some have a more or less strong red tinge. Everything that lies underneath is covered, including possible Merle areas, regardless of whether they are large or small. Such dogs are also called "Hidden Merles" (see below) due to the covered Merle color.

It used to be thought that the genetic expression of Harlequins/Fawnequins & Minimal Merles is very rare. Today it is assumed that it was probably the first mutation that led to the later expression of the known Merle variants. Here is the longest A-Tail attachment. Changes usually lead primarily to further shortening, which explains the other Merle variants. As Minimal Merles, this genetic variant managed to spread, unnoticed due to its often hidden appearance. It is often astonishing when (even among FCI) breeders a Harlequin/Fawnequin is suddenly born unexpectedly, because Minimal Merles can also have this color variant as offspring; they both have the same genetic status with m/Mh. Breaking down the alleles can shed light on the issue. But it also shows the danger that ignorance can lead to the birth of Double Merles with health problems (see below), if you do not safely rule out the possibility of having a Minimal Merle through a Merle test before mating, which shows how important this test is! But here too, I have not yet come across a case where a collie with the genetic condition m/Mh has any hearing or visual impairments.


 Mosaic Merle (m/…/...)


Mosaic Merle is a kind of mixed form of different Merle alleles. The changes at the Merle alleles are comparatively unstable. Small deviations can sometimes occur during embryonic development, which is characterized by many cell divisions until the final individual grows. Extensions on the A-tail rarely occur. More often can something break away, so that the A-tail becomes shortened. So it can happen that, in addition to the original Merle variant, a different Merle variant multiplies. In genetic testing, you can find three or more alleles at once instead of two. Normally the original variant remains the most represented, and is then referred to as a major allele. Added variants are referred to as minor alleles; to make them easier to identify, they are placed in square brackets. For example, if the Merle allele is shortened in a Classic Merle (m/M), the Merle allele (M) changes to an Atypical Merle allele (Ma), the result would be: m/[Ma]/M. Rarely there is another additional shortening, for example a Cryptic Merle allele (Mc), then this would also be added in brackets m/[Mc]/[Ma]/M. If there is a plus sign somewhere there, it will of course also be added. If there is an extension of the original Classic Merle allele, a (Mh) allele would also be possible, also put in brackets. There can also be shortening and lengthening at the same time. The respective number of base pairs (bp) is often added, for example in a round bracket.

Even if three or more alleles are named in mosaicism, this does not mean that they are all found in one cell. It remains the double set of chromosomes (diploid) with 2 alleles in each body cell, just in a different composition. In the examples mentioned, in addition to the original M/m variant, cells with m/Ma or m/Mc or m/Mh can also be found. In order not to make things unnecessarily complicated, you summarize the result in one by writing the alleles mentioned one after the other and putting the minor alleles in brackets. By the formation of eggs and sperm cells, the set of chromosomes in each cell is halved (haploid), so you find sex cells (gametes) with all possible variants. In these examples, in addition to cells with an "m" or "M", you would also find cells with a "Ma" and/or "Mc" or possibly also with an "Mh". For male dogs, it may also make sense to provide a semen sample for examination instead of a cheek swab.

According to current knowledge, Mosaic Merles are completely normal, healthy dogs. When it comes to mating, the same rules apply as before, except that it makes sense to only breed them with Merle-free dogs. This also corresponds to the requirements of the legislature.


 Mosaic Merle (m/[Mc]/M):

("Sunhills Collies Indigo Lagoon" by Mirjam Kessler)


Hidden Merle

The term Hidden Merles summerised all variants of Merles, which cannot be indentified from their appearance (Phänotyp), although they are carriers of Merle alleles. The bottom line is that they show the dangers of what can happen when genetic status is not known. If you breed such Hidden Merles with other Merles, especially if they are carriers of the Ma+ or M or Mh alleles, then so-called Double Merles (see below) can be born, with the risk of hearing and visual impairments.

The danger exists especially by Minimal Merles, when the small merle areas are either not noticeable or have been covered by White. It doesn't matter whether it is the normal White (Irish Pattern) on the collar and legs or whether there is a more extensive white coloring due to a White Factor (Piebald) (more extensive on the legs and often under the belly) or, in the case of White Collies, even covered over the further body, except the head. In this way, the Merle of Classic Merles could also be covered, but this rarely happens, as the basic color still appears as patches. The E-locus, which is very rare and undesirable in Collies, can also cover the body (and nose) in a dominant form with a reddish-yellow color, which at first glance resembles a Sable. Merle could also theoretically be covered by D-factor (Dilute), which is rare and not required in Collies (see Maltese Blue below).


E-Locus (e/e): 


In most Sable Merles, the Merle pattern is only visible in the early stages after birth. If the expression is not that strong (or is covered by White), then it can sometimes be difficult to recognize it, even at such a young age. As the puppies get older and at the latest in adulthood, Sable Merles are rarely easy to recognize. Sometimes they have a paler Sable or a more or less large spot of color in the eye or a complete staining towards amber coloring, but this is not a must. Since it is of utmost importance for the new owners of the puppies to know whether they have a Merle allele, such puppies must definitely be tested for Merle. It can also make sense to test the entire litter in order to be able to reliably determine the alleles in the individual puppies.

But the other way around, with a Merle dog (especially with the alleles Ma+ or M or Mh) you always have to be careful that there is never a planned or unplanned mating with another Merle, even across breeds. If you comply with the law, regardless of the version (Merle variant). One have to know that there are many breeds (as well as Collies) where Merle is not always obvious. Just like with other carriers (such as MDR1, DM, PRA, GCS etc.) you always make sure that there is no mating with other allele carriers in order to avoid the birth of puppies with health restrictions.

In general, it is always important to ensure the genetic status before mating so that no puppies with defects or limitations can be born, as our breeding regulations also stipulate.


Dilute Spots (m/M)


Very rarely, Classic Merles can lighten towards White in one or more spots or patches, but this has nothing to do with the Harlequin/Fawnequin variant, even if it looks like it. So it remains exciting to see what else nature produces. This again shows how important a Merle test with allele determination is.


Double Merle (M/M)


Similar to many other genetic mutations (e.g. MDR1, DM, PRA, GCS, etc.), you should not breed two Merles together so that no affected puppies (M/M) can be produced. Theoretically, this applies above all to the allele carriers of Ma+, M, Mh; In practice, however, this applies to all Merle allele carriers as long as the law fundamentally prohibits the mating of two Merle carriers, even if, according to the current state of knowledge, no puppies with health problems are to be expected, by matings with the allele carriers of Mc, Mc+, Ma. If you breed the other Merle variants with each other, there is a 25% probability that puppies will be produced, that have hearing and vision limitations, including deafness and blindness. Labogen has designed a nice table on its website, which can be found at the bottom of this link: .

Such Double Merles are also called "White Tigers" because they like to have large areas of White, including areas of the head. This makes it easy to distinguish them from the White Collies, which always have to have a colored head, this is why they are also called Color Headed White (CHW). The White coloring of White Collies is not due to Merle (see above)!!!
Affected Double Merles / White Tigers not only have a loss of pigment (leucism) in their fur, but can also have loss of pigment in their skin, inner ear and eyes. Where the skin is affected, it appears pinker and in areas not covered with fur, such as the nose, they are more sensitive to UV light when exposed to sunlight. If the nose itself is affected, it also turns pink, as do the affected lips and eyelid edges. In the inner ear, the lack of melanocytes disrupts the structure of the normally well-supplied vascular layer (stria vascularis) on the outside of the cochlea. The result is the lack of development of the sensory hair cells, which normally absorb and transmit sounds like antennas. Depending on the severity, this can lead to inner ear hearing loss or deafness. Affected eyes tend to turn an unnaturally light blue (significantly lighter than the blue found by Blue Merles) with sometimes dark pupils. Normally, the eye is protected from too much light and glare by the pigment stored in the iris. A loss of pigment there can lead to sensitivity to light. The iris can lighten so much, that it becomes transparent and the eye appears pink because you can see directly through it to the blood vessels of the retina, at the back of the eye. A lack of pigment in the choroid causes it to become significantly thinner (like the vascular layer in the inner ear). It appears that angiogenesis (the formation of new blood vessels from existing ones) is significantly reduced, according to Olivia Schatz (Schwab & Haas 2018 Uni Graz). 
It is therefore essential to avoid mating two Merles (even across breeds) if this could result in puppies with limitations or a complete lack of hearing and vision. It is all the more important to know the Merle Status of each dog so that its responsible owners can take early influence to avoid matings that are harmful to the health of their offspring (whether planned or not). Special attention is also paid to the Hidden Merles (see above), dogs whose Merle factor cannot be easily seen. The same applies to the Minimal Merles. Responsibel breeding clubs, like ours, ensure that the breeding dogs are tested for Merle (as well as other mutations such as MDR1, DM, PRA, GCS, etc.) before mating. The new tests definitely make sense for Merle, with a precise breakdown of the alleles so that we know what can be passed on to the offspring. In addition, buyers will be informed and instructed accordingly.


Affected Double Merle (M/M) (most of them show severe hearing and vision disabilities - therefor they are forbidden in Germany and some other countries!):



Inheritance Merle


Due to the legal situation, I have not made any further subdivision of the variants here. For better understanding, I have also entered the forbidden pairings; They may not be exported under any circumstances, not even as breeding partners:



Merle (heterozygot)   (permitted)


50% Merle-frei +   50% Merle (heterozygot) (permitted)

Merle (heterozygot)

25% Merle-frei +   50% Merles (heterozygot)  + 25% Double Merle (forbidden!)*

Double Merle (forbidden!)*

50% Double Merle (forbidden!)*    + 50% Merles (heterozygot)





100% Merle-frei

Merle (heterozygot) (permitted)

50% Merle-frei +   50% Merles (heterozygot) (permitted)

Double Merle (forbidden!)* 

100% Merles (heterozygot)


*Matings in which Double Merles can be born are prohibited in Germany and some other countries. The legislator does not differentiate between the different variants and does not allow any exceptions for the variants in which no damage to health is to be expected, such as Mc/Mc, Mc/Mc+, Mc/Ma, Mc/Ma+, Mc/M, and Mc+ /Mc+, Mc+/Ma and Ma/Ma. After that, only in very rare cases by the combinations with the variants Mc/Mh, Mc+/Ma+, Mc+/M as well as Ma/M, Ma+/M  are White areas and hearing impairments possible. There is a medium risk of White areas and hearing and visual impairments with Mc+/Mh and Ma+/Ma+. There is a high risk that puppies may be born with large areas of White in combination with an increasing risk of hearing and visual impairments by Ma/Mh, Ma+/M, Ma+/Mh and M/M, M/Mh, Mh /Mh. All matings with increased risk must also be avoided in countries where a legal situation like ours does not exist. Because our associations founding and headquarter are in Germany, the legal German regulations apply, so that Double Merles, regardless of the variant, are generally prohibited. They also cannot get a breed license. Should the legal regulations change one day, we will discuss adjustments in the breeding committee.


Fever Coat


Despite the appearance of brightening, Fever Coat has nothing to do with Merle. If there is a (usually harmless) infection or others suspect a lot of stress while the puppy is growing in the womb, a so-called fever coat can occur when the pigments for fur coloring arrive. As a rule, the head is normally intensively colored, sometimes also down to the shoulder area and forelegs, while the fur on the rest of the body is brightened to a greater or lesser extent. Often it is just a slight nuance. This effect is only temporary. At the next coat change (at the latest in adult fur), the pigment forms normally again, with normal color.


Maltese Blue / Maltese Gray (d/d):


By these collies, the colors appear diluted. Particularly affected are the areas of fur colored by Eumelanin, which appear lightened due to the dilution of the color pigments. By Tricolors, for example, the fur and nose appear grayish. Here and there it is reported, that the areas colored by Pheomelanin (reddish-brown tan markings) also lighten slightly and then appear cream colored instead of tan. The white markings (collar, etc.) are normally developed. In the past, this color variant was incorrectly assigned to the Merles, more precisely the Atypical Merles. But they have a normal black nose. One now know about the genetic cause, which has nothing to do with Merle. The D-locus, the so-called recessive dilution gene, causes lightening when it is homozygous (d/d), i.e. when the dog has received it from both parents. This is also the reason why this color variant is so rare, as the gene does not appear to be widespread in collies and two always have to meet, to become visible phaenoptypical. However, it can also spread unnoticed. According to the current state of knowledge, supported by the statements of Dr. Leigh Anne Clark, there are no health restrictions for affected Collies, but it is still one of the undesirable color variants. If the dog had Merle factor at the same time, it would not be visible because it would be covered by the D-locus. That's why it's so important to always test so that you can't miss anything!


Maltese Blue / Maltese Gray (d/d):

 (photo: Leigh Anne Clark)


Gray Collie Syndrom (GCS/GCS):


Maltese Blue / Maltes Gray should not be confused with Collies, that are affected by the Gray Collie Syndrome (GCS), also known as Cyclic Neutropenia, because there is a dramatic decreas of the White blood cells (leukocytes) every approximately 11 days. Our breeding regulations exclude the birth of such dogs, but I would still like to briefly talk about them for a better understanding. They also have grayish fur (usually more brightened as Maltese Blue / Maltese Gray and it can also turn beige after the coat changes), but the nose is usually even noticeably lighter and the tan markings are missing. The dogs are usually in very poor general condition as they are very susceptible to infections. That's why they usually lag significantly behind in development compared to healthy littermates. Many do not reach adulthood but die from simple infections. The disease can only break out if a Collie receives an affected gene from each parent, as it is an autosomal recessive inheritance pattern.


Gray Collie Syndrom:

(photos: Cynthia B.)




Tickings (spotting) can often be found by Collies, depending on their basic color (in Sable or Tricolor, possibly brightened if a merle gene is present). These spots mainly occur on the front legs and paws, but in rare cases they can also be found over the entire body. If the collie is colored, you cannot see the spots on the colored areas (e.g. on the back) because they are covered by the normal body coloring. The T-locus is affected here. There are two variants. On the one hand the pigmented Tickings in the unpigmented White areas and on the other hand the Tickings as such. Tickings are usually not noticeable in the first few weeks of life. The inheritance is autosomal dominant, probably with incomplete penetrance as the intensity can change slightly. The Tickings have nothing to do with Merle.




 (photo: Beate Rosenbach)



Text sources (following the links you can find besides the original text also many interesting photos): 


Dr. Leigh Anne Clark (USA), Jacquelyn Evans & Dr. Allison Starr-Moss, written by Kathy V. Moll with the permission from the Collie Club of America Bulletin, Newsletter Collie Healthfoundation Summer 2014, page 12


Collie Health Foundation - Vartiationin Collie Colors - Collie Kaleidoscope:


Southwest Collie Rescue - Remembering "Hershey" with Gray Collie Syndrom:


collie-online, by Patrick Martin and a quote of Dr. Leigh Anne Clark: 


Leigh Anne Clark et al (2006):


Mary Langevin et al (2018):


Mary Langevin et al (2022):


Labogen Sonderausgabe Merle (2022):


Diplomarbeit von Olivia Schatz - Schwab & Haas 2018 Uni Graz:


Webinar Merle bei Verena Priller von der Düsseldorfer Hundeakademie 2023


Weiterführende Infos zum Thema Merle gibt es hier; bitte beachten, dass nicht alle Labore zur Testung bei uns anerkannt sind:


©Beate Rosenbach



American Collie