The color black appears when a horse has a black gene (is not solid red) and has no bay (agouti) genes. Since bay is so common in the equine gene pool, the black color is proportionately rare.
A quick word on the color "black".
There are two known pigments in the horse's hair: red and black.
"Solid" black is a rare color in the equine world because there are so many genes that modify it into "something else".
Spots: we're not going to address white spotting on this site at this time.
The most common modifier is the bay gene, which is present in most horses alive. The bay gene confines the black color to the mane, tail and legs of the animal (its points). When a red horse -- chestnut, sorrel, palomino, cremello --- has a bay gene, it is invisible, because there is no black to be expressed on the points.
A black horse with a cream gene is a smoky black, which may be mistaken for "brown", "dark bay", or "seal brown".
Another gene that can influence black color is the dun gene. When the dun gene is present in an otherwise black horse, it becomes a grullo, with a more or less mousy grey body with black points, a dorsal stripe and leg barring. We are not going to go any further into this gene, on this site, at this time.
But when the black pigment is present in a horse with no cream
genes, no dun genes, and no bay genes, finally you will see a solid black
horse. Even this color sometimes will bleach in the sun, etc. and show
tinges of brown, red or orange. But when the new coat comes in each
season, it will come in looking "true black" all over.
Text © 2000-2009 by Julia Lord and horsecolor.com
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