We’re all familiar with Art 101. The color wheel is comprised of three primary colors and all of the subsequent combinations forming the secondary, tertiary, and quandary colors. And we’re familiar with Biology 101 — life becomes more diverse and variegated due to genetics and recessive and dominant traits. Well, both fields help us understand the color of our favorite canines. From the Chocolatest of Labradors to the Greyest of Hounds, dog colors are determined by two particular pigments present in each breed’s genetics.
Dog breeds have a black pigment in their genes called Eumelanin which expresses itself in a dog’s coat color, nose color, and eye color. This will determine how “black” a dog’s coat is or if they have any black markings on their coat at all. This pigment is the default coloration which explains why most dogs have black noses. However, Eumelanin can be altered slightly so that it produces a pigment closer to gray, brown, or light brown. These hues respectively are called “blue,” “liver,” and “isabella.” If a dog’s Eumelanin goes more liver, for example, not only will their coat color be affected but also their nose color and eye color. A dark brown eye (generally standard in a dog) would become more of a golden ochre in a liver-hued dog, and their nose would be more of warm brown. Liver and Black are the primary coat colors in the Eumelanin set while “blue” and “isabella” coats are known as “dilutes” as they are merely watered down versions of the black and liver respectively. It should also be noted that if a dog’s Eumelanin tells a patch of fur to be liver, then that will also hold true for all other pigmented information in a dog. So, it will not be possible for a liver colored dog to also have a true black nose because all data informed by this pigment will stay consistent.
Dogs also have a secondary pigment which is red. This is called Phaeomelanin. Unlike Eumelanin, the only information affected by Phaeomelanin is coat color; even if the presence of Phaeomelanin is more pronounced in a dog than their Eumelanin, they will still have black noses and darker eyes. Also, Phaeomelanin only expresses one color — red — as opposed to two groups of color like Eumelanin’s liver and black. Actually, “red” is a bit deceptive as a descriptor here. Although it does include dogs with truly red coats (in the way an Irish Setter does,) it also includes the gamut of hues that can be produced with that red pigment including golden tans, yellows, and oranges. A dog’s genetics determines how pronounced the Phaeomelanin is, and how dense the hue of their coat is.
The distribution of these pigments within each dog is a bit random. Sometimes you’ll have banded coats where red and black hairs spread close together as when the roots of a person’s hair reveal their natural hair color against the dyed hair color. These combinations produce muddier dog coat looks thanks to the variety of different colored follicles. While families tend to have similar coat patterns, a stray spot here and there will differ from dog to dog. The distribution of colors, too, can be variant ranging from an absence of a pigment to an overabundance of it. This is how every coat color and combination is made apart from one exception.
White, the presence of all color in the visible light spectrum, is the absence of all color and information in a dog coat. Dogs have white coats whenever both of these pigments are inhibited or whenever the Eumelanin and the Phaeomelanin are extremely weak. For example, whenever a dog has a completely white body and a black nose and darker eyes, it means that the Phaeomelanin is dominant but unpronounced. You may notice that a dog in this instance is more “ecru” than white. If this is the case, the Eumelanin still knows to make the nose black and the eyes dark because it is responding to the Phaeomelanin’s dominance. However, in the case of albino dogs or breeds where the genetics don’t clearly delineate a dominant/recessive relationship, the eyes will be blue and the nose will likely be pink because the Eumelanin is not affecting those traits. A true albino dog would have red eyes, but it is more common to find dogs with weakened traits as opposed to the anomaly of actual albinism. “White spotting” — technically termed epistasis — in a dog refers to white patches that lay on top of any Eumelanin or Phaeomelanin on a dog. This means that any dog coat color can be speckled with white regardless of their dominant pigmentation.
This is just scratching the surface of the biology behind dog coloration, but these are the fundamental principles upon which the science is based. Like the primary colors on the color wheel, small bits of pigment help determine a wide variety of color.