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From Bay to Buckskin: A Practical Guide to Color Genetics

· The Cavvy

Horse color can be fascinating, confusing, and sometimes misunderstood in sale listings. Understanding how color is inherited helps you market accurately, buy confidently, and avoid surprises in offspring.

The Veterinary Genetics Laboratory at UC Davis has excellent educational resources on equine coat color genetics. You can explore their information here:

https://vgl.ucdavis.edu/resources/horse-coat-color

Let’s break this down in practical terms.

It Starts With Base Color

Every horse starts with a base color controlled by the Extension gene, often called the Red Factor.

There are only two base pigments in horses:

  • Black
  • Red

If a horse is genetically ee, it will be chestnut because it cannot produce black pigment.

If a horse carries at least one E, it can produce black pigment.

Next comes the Agouti gene, which controls where that black pigment is placed.

If a horse has black pigment and carries Agouti, the black is restricted to the mane, tail, and legs. That creates a bay.

If a horse has black pigment and does not carry Agouti, the coat can be solid black.

So at the most basic level:

  • ee = chestnut
  • E + A = bay
  • E without A = black

That is the foundation of all other colors.

Dilution Genes Modify the Base

Once you know the base color, dilution genes can lighten or alter it.

Some of the most common include:

Cream
One cream gene can turn:

  • Chestnut into palomino
  • Bay into buckskin
  • Black into smoky black

Two cream genes create double dilutes like cremello or perlino.

Dun
Dun lightens the body but leaves primitive markings like a dorsal stripe and leg barring.

Champagne
Champagne dilutes both red and black pigment and often results in lighter eyes and freckled skin.

Pearl and other rarer dilutions also exist and can be identified through testing.

UC Davis offers a full coat color panel that includes these genes:
https://vgl.ucdavis.edu/panel/horse-coat-color-panel

White Pattern Genes

White pattern genes do not change pigment. They add white markings.

Common patterns include:

  • Tobiano
  • Frame Overo
  • Splash
  • Sabino

One important note for breeders is Frame Overo, also known as LWO. When two copies are inherited, it results in Lethal White Overo syndrome.

Information on LWO testing can be found here:
https://vgl.ucdavis.edu/test/lethal-white-overo

If you are breeding patterned horses, genetic testing is not optional. It is responsible management.

Gray Works Differently

Gray is a dominant modifier.

A gray horse is born its base color and gradually loses pigment over time. Many grays eventually appear white, but genetically they are still their original base color underneath.

If one parent is gray, each foal has about a 50 percent chance of inheriting gray.

Gray does not skip generations. If a horse carries gray, it will gray out.

UC Davis explains gray testing here:
https://vgl.ucdavis.edu/test/gray_presence_absence

Why This Matters in the Marketplace

Understanding color genetics helps you:

  • Market horses accurately
  • Avoid genetic health risks
  • Predict potential foal colors
  • Provide transparency in listings

It also prevents common mistakes like labeling a smoky black as black, or assuming two colorful parents will automatically produce a colorful foal.

If you want to experiment with potential crosses, this foal color calculator is a great tool:

https://avian2.animalgenetics.com/Equine/CCalculator1.asp

The more genetic information you enter, the more accurate the predictions will be.