Grey (G) is a modifier that depigments a horse's body color over time. Greys are born a color and through their lifetime turn various colors of grey. Greys have dark skin and dark eyes. They go through many different graying phases. The speed at which a horse greys out varies. Dapple grey, rose grey, white grey, steel grey, etc are all names for various stages of greying. Fleabitten greys have small dark flecks on a white coat. Bloodmarks are reddish dark areas on a fleabitten grey. Greys often go a darker color before starting to go lighter and the legs will usually be the last to grey out. Most horses referred to as being white are actually grey.
A grey is still the color that the grey washed out. So a palomino that was depigmented to grey can still produce cream dilute foals. Grey pintos are still pinto. Grey does not affect white markings, but as the grey gets lighter the white markings seemingly disappear as they blend together. The markings can be seen again when they're wet.
Grey foals have what is called hyperpigmentation, meaning they will be an adult color when they're born. Usually foals will have a foal color that looks different from their adult color. For example, bay foals will have greyish looking legs that will eventually shed black. But a bay foal that will turn grey will have adult-like black legs. Grey foals often have grey rings or "goggles" around their eyes.
Greying progression of a Welsh Pony mare
Grey is dominant so for a horse to be grey it must have at least one grey parent. Because of this grey would have to be reintroduced into the breed for there to be a grey Chincoteague Pony again. A heterozygous (one copy) grey will have grey offspring statistically 50% of the time. Fleabits and bloodmarks are more common on heterozygous greys. A homozygous (two copies) grey parent will only have grey offspring. They will likely go grey faster. There is a genetic test available for grey. Greys have a high likelihood of developing some type of melanoma. The grey mutation is quite old and has been traced to at least 2,000 years ago.
Grey has a long history in Chincoteagues despite not longer being found in the breed. Grey may have existed in the early days and may be one of the original colors. A 1891 article in the New York City newspaper The Sun stated that the ponies "are most frequently black, gray, sorrel, or dun." However, Leonard D. Sale wrote in 1896 in The Horse Review of Chicago that, "I have never yet seen a grey, piebald, dun, or yellow purely bred island pony." A 1912 Baltimore Sun article stated that the ponies were "white sometimes". A 1916 article in The Country Gentleman stated there were greys in the herd. A 1923 St. Petersburg Times article described the ponies as "bay, gray, dun, black, and sorrel". American Wild Horses wrote in 1936 that 50 years before the ponies "were all solid colors: browns, bays, blacks, greys, chestnuts." The only Atlantic feral herd that currently has grey is Ocracoke Horses thanks to 1970s outcrossing with a grey Andalusian stallion named Cubanito.
Clarence Beebe brought grey into the Beebe Ranch herd sometime in the 1950s. The grey mares Beaufort Misty and Beaufort Blue Bell were bred by Beebe Ranch. The mares have Welsh Pony characteristics so the grey was likely from from Welsh outcrossing.
A postcard dated to the 1950s shows several greys photographed on
Assateague. Another possible grey was caught on video by the show Wild
Kingdom in 1967.
The grey Arabian stallion Skowreym was loaned to the Chincoteague Volunteer Fire Department in 1967. Reportedly many of his 1968 foals were grey. Skowreym was heterozygous for grey so statistically half of his foals would have been grey.
A 1978 article on the Mustang introduction of 1977 mentions that grey Mustangs were in the group selected to be released on Assateague.