Collie Coat Colours
The Rough and Smooth Collies come in a few different coat colours. These colours are the same all around the world, however the Kennel Club breed standard for the Collie varies between countries. Because of this, some colours are not bred as frequently in the UK or Europe as they are in America, even though they occur naturally. These colours might be available infrequently, but it is recommended you don't get your heart set on a coat colour that may only show up every few years! The chart below shows the colours each country recognises in their breed standard, and therefore the colours usually available and which can be shown in conformation shows.
UK and FCI Standard
The chart above shows the 'recognised' colours in each country, and the colours which can be shown. However, all of the colours occur naturally occur within the Collie gene pool.
FCI standard countries include Europe and Australia.
Next, we will take a look at each colour.
Sable can range in colour from a light straw colour to a deep mahogany. Light straw is undesirable, a golden - mahogany tone is favoured. Sable can come in two forms - 'Pure' Sable, and Tri-Factored Sable. Pure Sables are usually lighter in colour, and have two copies of the Sable gene.
This is the other form of sable, sometimes called 'shaded sable' or 'mahogany sable'. Tri-Factored sables are often darker, may have a dark widow's peak marking on their foreheads, and often have a 'cape' of black banded hairs. Their colour can change with their coats, and they sometimes become darker as they age. Tri-Factored sables are called this as they carry a Tricolour gene, which is recessive to the Sable gene, but interacts with it in such a way that it is able to show through the Sable (hence the dark cape).
Tricolours are black dogs, with tan points and the usual white Collie markings - three colours, hence the name. Their tan points can vary in colour intensity, some being quite pale, some being richer.
Blue Merles are genetically Tricolour Collies, that have inherited the Merle gene. The Merle gene can turn parts of the coat lighter, making them grey, and sometimes can delete pigment entirely to make patches of white. The Merle gene itself has a tail called a 'Poly-A tail', and the different lengths of tail produce different effects. Because of this, Blue Merles can come in a wide variety of colours, from almost completely white, to pale, silvery blue, to darker grey and even sometimes appear almost completely black (Tricolour). You can read more about this here. Their black patches can also vary in size, with larger patches, smaller 'mottles', or larger sections that may even cover whole body parts! The most desirable colour of Blue Merle, and the one requested in the Breed Standard, is for a light silver, splashed and marbled with black patches of smaller or larger size.
The Merle gene can also affect Sables, although the effects are slightly different. Merle can only affect black pigment, called 'Eumelanin', whereas Sable is caused by red/brown pigment, called 'Pheomelanin'. Because of this, Merle can't affect the majority of the Sable coat, and very often the Merle is not visible at all on Sable Merles. Tri-Factored Sables Merles, who have a tri gene causing black banded hairs, can sometimes be recognised as Sable Merle. This is because the black parts of the hair can be affected by the Merle gene. So, a Tri-Factored Sable merle may have patches in their black banded areas, with these patches appearing lighter sable. To differentiate them from Sable non-merles, in our Collie drawings the Sable Merles have a small white patch, even though this is not realistic!
Colour Headed White
The gene that causes White Collies is called 'Piebald'. A White Collie will be genetically Sable, Sable Merle, Tricolour, or Blue Merle, with the Piebald over the top. Because of this, they often have coloured markings on their head and face, and sometimes patches on their bodies. We call them 'Colour Headed White' (often abbreviated to CHW) for this reason. This means you can get Colour Headed White Collies with any of the Collie colours on their heads, or in body patches.
Homozygous Merles are often referred to as 'Double Merles', and also incorrectly referred to as 'Double Dilutes' or 'Lethal Whites'. They should not be confused with Colour Headed White Collies, which do not suffer from the same effects.
Homozygous Merles are born when two Merle dogs are mated together, and some of the offspring inherit two Merle genes. They often are almost completely white, and are usually blind, deaf, or some combination of the two. Homozygous Merles often have eye problems such as microphthalmia, coloboma, starburst pupil, or lack of eyeballs. When two Merle dogs are mated, not every puppy in the litter will inherit two Merle genes, and become a Homozygous Merle - on average 25% of the litter will be born this way. However, due to the risk of producing Homozygous Merles, and the huge impact on Quality of Life they experience, Merle to Merle matings in Collies should not take place.
It is important to know why these defects happen. Deafness is thought to occur as a result of lack of pigment on the hairs inside the ear, caused by the excessive whiteness. Occular (Eye) defects are believed to occur as, when an embryo is developing, the cells that go on to produce coat colour come from the same area as cells that develop the sensory and nervous system. The two Merle genes can then cause congenital eye disorders, along with damage to hearing.
We can see that the effects occur when two Merle genes are inherited, but these issues do not affect normal, single Merle dogs such as with the Blue Merle or the Sable Merle coat colour. Single Merle Collies do not suffer from the congenital occular or auditory defects that affect Homozygous Merle Collies. The Kennel Club (UK) will not register the resultant puppies of a Merle x Merle litter.
In the Rough and Smooth Collie breeds we have two 'building blocks' of coat colour - sable and tricolour. All other coat colours are based on these two colours. We can split these colours further into the two alleles they are produced by, both on the A locus.
Sable vs Tricolour
In the A locus, sable is dominant over all 4 of the alleles in this series, although the collie breed likely only has two in the gene pool today - sable (Ay) and tricolour (at).
This means if a dog inherits one copy of Ay / sable, the dog will be sable.
However, Ay / sable is incompletely dominant over tricolour / at. This is what causes the tri-factored sable coat colour. The tricolour gene is suppressed by the sable gene but some of it is 'showing through' the coat. That is what causes the black hairs on tri-factored sables.
That means there are 3 combinations a collie can inherit on the A locus.
Ay / Ay (pure or homozygous sable)
Ay / at (tri-factored sable)
at / at (tricolour)
A merle collie is just one of those combinations with a merle modifier over the top. Merle is a pattern that only affects the black parts of the coat (otherwise known as eumelanin). Merle collies can either be tricolour / blue merle, or sable merle, but as the M allele only affects eumelanin, these mostly appear normal sable.
Merle is dominant, therefore if a collie has a copy of the merle gene it will be merle, and merle can't be carried (as it is dominant and will always be expressed)
Sable merle collies will be one of the following combinations:
Ay / Ay M / m (pure or homozygous sable, merle)
Ay / at M / m (tri-factored sable, merle)
Blue merle collies will be at / at M / m (tricolour, merle).
Double merle dogs can have any combination of Ay and at and will be M / M.
White Collies, White Factor and White Markings
Irish spotting is the gene that causes the classic collie markings: including the white collar, white feet, and tail tip, among others. All collies have two copies of the gene (this means they all express irish spotting to a greater or lesser extent). Irish spotting is denoted as si, however it is thought to be located on another locus to the S series.
White collies are caused by a gene for piebald. Some collies have no piebald gene (S), some have one piebald (sp) allele (they will be white factored) and some have two copies of the sp allele (this is what creates white collies). White factored dogs aren't white but often have white above the hock.
So knowing all collies have 2 alleles for white spotting (si), here are the combinations we have on the S locus:
si / si S / S (irish spotting, no white factoring)
si / si S / sp (irish spotting, white factored)
si / si sp / sp (irish spotting, white collie / extended white factoring)
Breeding two white factored dogs together can produce collies of all the S locus varieties.
In the diagram below, the white factored collies are represented as the tri coloured dogs that have white above their hock.