Grey is a Dominant, requiring only one gene from one parent in order to take effect. Technically, gray is not a true COLOR gene, but rather, a COLOR-REPLACING gene.

Gray gradually replaces whatever other color(s) that may be present in a horse's genetic makeup.

This gray mare's foal is already showing signs of turning gray.

GRAY HORSES AT BIRTH:

Horses with the grey gene can be any color or color pattern at birth (yes, including pinto and appaloosa!) depending on their other color inheritance.

A horse must have at least one Grey parent to be Grey, and if a horse inherits one Grey gene it will be grey, and at least 50% of its offspring will be gray.

Homozygous Greys have two gray genes, one from each parent, and their offspring will turn Grey 100% of the time.

These pinto foals have a 50-50 chance of inheriting their mother's Gray gene

"Cinnamon" owned by Nan Moore of Florida

EARLY SIGNS OF GREYING: Sometime in early life, they begin to "roan" or develop a sprinkling of gray on the backs of their ears and around their eyes.

At this stage they may look like reverse raccoons, with big grey/white circles around their eyes, although the "goggles" look is not always that obvious.

A white area, such as a blaze on the face, may seem to "leak out" spreading and growing irregularly, like spilled milk.

A "Normal" Bay foal who will stay bay is born with light-colored legs. Compare this to the foal at left, who will turn gray like his mother.

At right: Early graying signs: gray shows first around the eyes and backs of the ears. The face turns light, too, which is not seen on roans (which these foals are often mistaken for)

Gradually the gray takes over, and the entire horse turns gray. Eventually, most grey horses fade to pure white. (Roan, which this stage of gray is most often confused with, is not progressive, and does not involve graying on the face)

At this stage Greys may still be confused with Roans.

Rainer Stabenow on his Egyptian Arabian gelding

"Pure White" Gray Shire at Grass Valley Draft Horse Classic

 
"Pure white" Gray Shires at the Draft Horse Classic in Grass Valley, CA

Joachim Stabenow with his Polish Arabian, Gypsy

Fleabitten grays are believed to be heterozygous for grey, meaning they have a 50-50 chance of passing the gray gene on to their offspring.

Although most grey horses have dark skin, there is a variation of the grey gene that causes the skin itself to lose pigment as the animal ages. This is sometimes called "PINKIE", and is common in the Lippizan and Arabian breeds.

WHY DO SOME GREYS RETAIN DARK POINTS AND OTHERS' POINTS LIGHTEN WITH THEIR BODY COATS? WHY DO SOME TURN WHITE QUICKLY AND OTHERS REMAIN DAPPLE GRAY FOR A LONG TIME?


All grays will turn gray the same way (over time, progressively), but the amount of fading (steel gray vs. very white-looking) has to do with the proteins or lack thereof being made in the coat. Just as some people gray to a very white and some stay a darker gray, horses vary too, and it's probably due to genetic variations from the parents.