Above: The Buckskin horse can be distinguished from the Dun primarily through lack of a dorsal stripe, also a gold or yellow body color as opposed to the more Tan shades of dun. What matters most in determining whether a horse a Buckskin or a Dun is what the blood carries. Are the parents creme, dun, both?

Pictured above: A simple Dun on a Bay base

According to the worlds leading equine genetics experts there are three basic coat colors, (not including the much debated brown). These colors are Chestnut, Bay, & Black. Bay is actually a combination of Chestnut and Black, with the “Agouti” gene restricting black coloring to the points leaving the body a red or brownish red color. When other genetic modifiers are added to bay it has its own results different from red or black alone. So for all intents and purposes it is a base color of its own, although made up of black and red.

So, If there are only three base colors in existence there can only be modifications of those. Greys must be of one of the thre bases, so must pintos, roans, & spotted horses.Those are pattern genes. Now for the dilutions.

There can also only be dilutions of Red, Bay, or Black (palomino, buckskin, smoky black, dun, grullo, red dun)

THE DUNS

The Dun Factor gene Lightens the “basic” coat color, but leaves the points (mane, tail, & lower legs) their original color. In addition a dun factor horse will have a distinct dorsal stripe (as in the term “line-back dun”). There are three possible Dun factor dilutes.
CHESTNUT+ DUN = RED DUN
The body is diluted to a lighter shade of red while the mane, tail, and lower legs are left their original chestnut color. Also the dun factor markings will appear darker red.

BAY + DUN= DUN
The body is diluted to some shade of tan, leaving the points and dorsal stripe black. Other Dun factor markings may include a shoulder stripe in addition to the Dorsal or “eel stripe”, Zebra striping on the legs or white frosting on the mane & tail.


BLACK + DUN = GRULLO (black dun)
In the Grullo one part black gene & one part dun gene combine & the body color is diluted to an unusual mousy grey color with black points, face & dorsal stripe. As black is the rarest of the base colors, naturally grullo, the black version of dun is the rarest of these dilutes.
The closer the parents coloring is to grullo (dun, black, or grullo) the better the chances of a grullo foal. Two Grullos will always result in grullo. There is no double form of dun. Any difference in horses with one or both dun parents has never been reported. A black bred to a grullo will ALWAYS result in grullo, because you are breeding two black horses, one with dun factor which is a dominant gene, and always modifies the color. It is also possible to result in grullo from an array of different combinations. The minimal requirement to result in grullo is one parent MUST be a dun and one parent must have black points.

Black is recessive – you need a “double-shot” (one from each parent) to result in black. (or a black dilution. Both parents must CARRY AND THROW the black part of the gene to produce a black foal (or a black dilute, such as grullo)In order to be genetically “black”, the horse’s code must be aa – two black recessives.

THE BUCKSKIN GENE (CREME)

Like the dun factor gene, the crème gene lightens the “basic” coat color, unlike a dun factor horse a crème dilute horse does not have a line down its back, or any of the other “DUN FACTOR” markings. It is possible to carry both crème and dun. As seen in the BUCKSKIN DUN (also called DUNSKIN) or PALOMINO DUN (also called DUNALINO).

The crème gene is “incompletely dominant” meaning that it acts differently on different pigments. While in the chestnut base the body will lighten to some shade of gold or yellow, the mane and tail are lightened to a shade of gold anywhere from matching the body to white. In bays the body color is gold or yellow, and the points, mane and tail are left their original black as it requires two copies of the gene to have any effect on black pigment.

Two doses (both parents contributing 1 creme gene) can result in double dilutes (homozygotes). Cremello on Chestnuts and Perlino on Bays
Other times Two palominos bred to each other revert to Chestnut, or two Buckskins to Bay. The only predictable way to breed palominos or buckskins is by a Double Dilute of the appropriate base color to be bred to Chestnut or Bay depending on whether palomino or buckskin is the goal.

CHESTNUT + CRÈME = PALOMINO
The body color is diluted to some shade of yellow or gold, the mane and tail can be the same shade as the body, or it might be nearly white.

BAY + CRÈME = BUCKSKIN
The bay base is diluted to a yellowish color, but leaving the points black.
The buckskin horse can be distinguished from the dun through lack of a dorsal stripe and also a yellowish color as opposed to the tannish color of a dun.
Buckskin is the result of bay + crème. Dun is a gene all by itself there is just no argument to make on whether a dun with limited dun markings is really a buckskin, It’s not.
What matters most is the genetic make-up, not necessarily what a horse looks like.

BLACK + CRÈME = SMOKY BLACK
Black is only modified when two copies of the gene are present. This is a difficult coat to identify, the crème gene lightens the black coat to something resembling off black or faded black. These horses are often mis-identified as brown or dark bay, making pedigree research very difficult. Again what determines the color is the genetic make-up of the animal.

It stands to reason that if this gene causes BAYS to be BUCKSKINS and CHESTNUTS to be PALOMINOS, then there must be a name for the similar dilution of black horses.