You might be surprised to know that some horses do not stay the same color for their lifetime. As if by magic some horses who are born one color, transform themselves into a horse that is often mistakenly referred to as being white.
Many non- horse people will see a gray horse out in the field and think of it as a white horse. In truth there are very few truly white horses, most are gray horses, those born a different color and who now sport white hairs where their colored ones use to be.
Horses who are going to go gray must have at least one gray gene. This is a dominant gene, so the horse must have one, or both, parents who are gray. A breeding of two non-gray horses can never produce a gray horse. A gray horse is distinguished from a white one because the gray horse still has dark skin, where as the white horse will have pink skin on its entire body.
If we look at gray as G and non gray as g, we see that a gray horse could be GG or Gg, all non-gray horses are gg. If we were to breed a non gray horse with a Gg horse we would have a 50/50 chance of getting a gray horse. If we bred a GG gray to a gg non-gray, all the off-spring would be gray, to read more about Gray genetics, see the link at the bottom of the page.
Any color of horse (other than white) can turn gray, even spotted appaloosas or pintos. The speed of which horses go gray is determined by other factors and genetics which we will not get into here. Typically they are born solid colored, even more so than a horse would who is a solid color. For example a chestnut foal who is going gray might have a bright chestnut color at birth where as a horse who will always be chestnut might look as thought it was slightly faded at birth and will brighten up in a few days. If a horse is going gray quickly the graying will start within a few days of birth, often being noticed on the muzzle and ears first.
At a few months of age you cannot see many signs that this filly is going gray, small changes are taking place around her eye, and on her muzzle. Photo by Author.
This is the same filly as the first photo, along side her mom, she is now steel gray in color, and you can see her tail is lighter. She would be 3 years old in this picture. Photo by Author.