Basically, horses are either red or black.
Coat pigmentation is determined by the presence, absence or relative proportions of the pigments eumelanin and phaeomelanin. Eumelanin is either brown or black in color, phaeomelanin is either a reddish or yellowish brown. In horses of genotype B+B+ the eumelanin – if it is produced at all – is always black. http://www.horse-genetics.com/horse-color-genetics.html
Then there are gazillions of genes to modify those into a rainbow of colors.
Let’s start with a red horse… (chestnut, sorrel)…
(above, my ten dollar pony, Knock’em Silly)
The mane and tail are either lighter or the same color as the body.
Liver chestnut (above) can look just like some versions of black modified by the silver gene (aka: silver dapple or taffy)…
Surfer Dude was a well known Chincoteague pony (that’s my pic of him at Pony Penning). He was tested genetically and found to have the silver gene, not liver chestnut. In other words, he is a black horse with the “silver dapple (not always dappled) or taffy gene. Silver lightens the black pigment to browns and blonds (hence the name Surfer Dude: he was an island pony, and blond).
“Sorrel” is used instead of chestnut by some horsemen, often in reference to a blondish, flaxen maned horse. Is it genetically distinct?
Check this page… http://www.horse-genetics.com/sorrel.html
The gene that makes chestnut horses chestnut is called the extension or E locus. Three alleles (forms) of this gene are known at present, labelled E+, e and ea. E+ is the dominant allele and the coats of horses with this allele contain black eumelanin pigment. The alleles e and ea differ slightly in their molecular composition but nevertheless is reported to have the same effect on horse color, causing a switch from the production of black eumelanin pigment to red phaeomelanin pigment. Chestnut horses are homozygous for either recessive allele, or of genotype eea.
Several genes affect the shade of chestnut, including flaxen (blond) and sooty (dark).
Add some black and an agouti gene and you get bay… (me on Saraf in the 80s)
Add a cream gene to your red horse and you get palomino…
Two cream genes and you get cremello…
Cream on bay gets you… buckskin.
Two cream genes on bay gets you perlino…
Add the silver gene to chestnut and you get…
…chestnut, it doesn’t affect red.
Silver on bay though, (red and black with an agouti gene) you get silver bay…
Champagne on chestnut gets you…
Looks like palomino… varies, like palomino, in shade from cream to deep gold.
Champagne on bay gets you… amber champagne. (looks a little like perlino, which is two cream genes).
Add roan to your red horse (chestnut) (white hairs scattered throughout)…
…and you kind of get a pink horse. (strawberry roan)
Roan on bay (red horse, black points from agouti gene) you get a red roan…
The dun gene on chestnut gets you red dun…
note the dorsal stripe, also zebra stripes on the upper legs are common, this is a primitive horse color.
Dun on bay gets you…
…looks like buckskin but it’s not. It’s a very primitive color, often marked by dorsal stripe, and leg stripes. Check out the stripes on this stock type horse…
Sometimes has a two-color mane (white outside, black inside like a reverse Oreo cookie)… like the Fjord above. Fjords often have their manes cut short, to stand up and emphasize the arch of their neck… and those manes are cut in fun patterns to show off the color.
A horse can have more than one modifying gene… pile up black, dun and silver and you get… (Icelandic pony)… http://colorgenetics.info/equine/gallery/dilutions/silver/blue-dun-silver-dapple
Oddly I have a huge plush pony rescued from a yard sale that looks just like that.
That is silver dapple/smokey black: silver gene, cream gene, black base color.
That Fjord cross is a dunskin. Fjords only come in dun (several shades). The other side of the family had buckskin (cream on bay). So this horse has cream, dun, red, black and agouti.
Icelandic: silver, buckskin, dun (bay base: red, black agouti).
They have no idea… supposed to be silver grulla (black, dun, silver)… but sire is buckskin so… smokey silver grulla???? (cream, silver, black).
She’s “Half POA, 1/4 Friesian, 1/4 Appaloosa” Phew!
Buckskin silver…(Icelandic pony)… bay, (red, black agouti), cream, silver. Looks like champagne.
Bay, dun, silver.
I will make a point that none of these silver horses are grey. Grey is a combination of white and dark hairs that gets whiter over time. Silvers and grullas are made of pewter/silver/iron colored hair.
Then there’s brindle…
Common in dogs and cattle, it’s uncommon in horses. So far, a few horses, like Dunbar’s Gold, have been discovered to be chimeras; fraternal twins, fused into one body in the womb. So breeding brindle horses does not get you brindle horses. But they are very cool.
And we haven’t even touched pinto, leopard complex, grey (all white patterns overlaid on horse colors).
Or zebra hybrids.
Donkeys have a whole ‘nother set of genes and colors, so mules (male donkey, female horse) come up with some fabulously weird colors and patterns.
Check out my pinterest boards on horse color here: https://www.pinterest.com/swordwhale/