Have you ever wondered how your horse came to be the color he is?

I will attempt to help, in very simple terms how this came to be.


always remember that genes come in pairs,

and that there are ONLY TWO base colors…


Every thing else is not an actual color, but a MODIFIER.

If you remember these two small ‘Color Rules’, it is much easier to catch on.

To begin,

lets start with the very basic of colors.

We can get into more depth (Grey, Champagne & Silver) at a later date.

So for now, I am only listing the base colors, plus the modifiers of Roan, Dun, Creme, and Agouti.


Chestnut/Sorrel (Red)

Strawberry Roan (Red + Roan)

Red Dun (Red + Dun)

Palomino (Red + Creme)

Looking at the above, we must remember that the base is all of them is Red.

What makes them Roan, Dun, and creme dilute are Modifiers. OR… a gene that modifies the red coat into something a little more special.

Red is a HOMOZYGOUS coat color. Meaning, a red horse carries two of the same genes for color. So, if you breed two red horses together, you will ALWAYS get a red foal from the mating.

However, it is recessive, so it can hide in a black base horse.

When we get to discussing modifiers, you will learn that the most common modifier of all, AGOUTI, does not affect red base coats. Meaning that a red horse can carry agouti, and not show it.



Smokey Black (Black + Creme)

Blue Roan (Black + Roan)

Grullo/Grulla (Black + Dun)

Bay (Black + Agouti)

Buckskin (Bay + Agouti)

The above are all black base colors.

The same as the red, it is the modifier that changes the color to something different that just black.

Black is slightly differant in that it can be HOMOZYGOUS or HETEROZYGOUS. (One gene or two genes for black.)

It is also DOMINATE, which means that if a black horse carries one red gene and one black gene, the horse will still be black to the eye. (SEE, the red gene can hide there.)


Let’s begin with the most common of all modifiers.


Agouti LIMITS black hair to the points. (Ears, legs, mane and tail).
It does not allow it on the body of the horse.
Black + Agouti = Bay.

Some black base colors can be changed by other modifiers,
but it is not possible for them to also carry agouti.
These colors have black hair on the body and not just on the points.
They include:
Grullo, Blue Roan, and Smokey Black.

Agouti can hide in a red based horse, as it does not affect the red coat.
The only way to tell if a red horse carries the gene for agouti,
is sometimes by the color of offspring, or by a simple hair strand test.
Red + Agouti = Red (It does not change)

Agouti can be homozygous or heterozygous.
If a horse is homozygous for agouti, it will never produce
Black, grullo, blue roan, or smokey black foals,
no matter what color the horse is bred to.
If the horse is heterozygous, 50% of it’s offspring will carry agouti.

Genetic experts have now found that there are over 30 variations of agouti.
It is now also being said that agouti is the gene that is responsible for
“Brown” horses.