produce gray foals. Prevalence Gray is common in many breeds. Today, about one horse in 10 carries the mutation for graying with age. The vast majority of Lipizzaners are gray, as are the majority of Andalusian horses. Many breeds of French draft horse such as the Percheron and Boulonnais are often gray as well. Gray is also found among Welsh Ponies, Thoroughbreds, and American Quarter Horses. All of these breeds have common ancestry in the Arabian horse. In particular, all gray Thoroughbreds descend from a horse named Alcock's Arabian, a gray born in 1700. The gray coat color makes up about 3% of Thoroughbreds. Gray also affects spotting patterns of pintos and leopard complex horses such as Appaloosas. Its effects wash out the contrast of the markings of these patterns, sometimes colloquially described as “ghosting.” Changes in the color of gray horses A gray foal may be born any color. However, bay, chestnut, or black base colors are most often seen. As the horse matures, it “grays out” as white hairs begin to replace the base or birth color. Usually white hairs are first seen by the muzzle, eyes and flanks, occasionally at birth, and usually by the age of one year. Over time, white hairs replace the birth color. The changing patterns of white and dark hairs have many informal names, such as “rose gray,” “salt and pepper,” “iron gray”, or “dapple gray.” As the horse ages, the coat continues to lighten, often to a pure white. Some horses develop pigmented reddish-brown speckles on an otherwise white hair coat. Such horses are often called “fleabitten gray”. Different breeds, and individuals within each breed, take differing amounts of time to gray out. Thus, graying cannot be used to approximate the age of a horse except in the broadest of terms: a very young horse will never have a white coat (unless it is a true white horse), while a horse in its teens usually is completely grayed out. One must also be careful not to confuse the small amount of gray hairs that may appear on some older horses in their late teens or twenties, which do not reflect the gray gene and never cause a complete graying of the horse. This change in hair color means that the same gray horse will appear to be a different color over time, sometimes resulting in a need to change the color