Grey:  Contrary to popular belief, grey is not so much a color as a color modifier. Grey is a dominant gene that causes the horse's natural coat color, whether it be bay, black, dun, or palomino roan, to slowly "depigment" as the horse ages, much like human hair, regardless of the color, "greys out" with age. Most greys go through a lovely dappled phase, ending up nearly white or sometimes fleabitten. Because grey is a dominant gene, all grey horses will have at least one grey parent. Foals usually show evidence of greying on their faces first, particularly around the eyes. Also, the tip of the tail on most greys lightens up early on.

Pictured below is Holy Bull, exhibiting the changes a grey goes through. Note how his face has already lightened in color even though the rest of his coat is still relatively dark in the photo on the left.

Pinto Patterns: Pinto is a term that refers to several different patterns of white. The patterns fall into two catagories, tobianos and overos. The overo catagory is really just a catch-all for non-tobiano patterns that includes frame overo, sabino, dominant white/white spotted, splash white, and manchado. A horse with a combination of tobiano and one or more overo patterns is known as a tovero.

The tobiano pattern is dominant, and it is characterized by white crossing the horse's topline, as well as by areas of color on the head, chest, and flanks. Most tobianos have normal face markings like stars and blazes, and they almost always have four white feet. Some minimally marked tobianos  appear to have only 4 stockings and no other discernable white markings.

Frame overos are characterized by having a predominantly dark topline with blocks of white on their sides and necks. Frame overos usually have large blazes or apron markings.The feet are usually dark, but may be white if combined with other pinto patterns, particularly sabino. The frame gene is responsible for "lethal white overo." Horses that are homozygous for the pattern (2 copies) die shortly after birth. Heterozygous frames are perfectly viable. (See below.)

Sabino is a pattern that comes in many forms. In its minimal form, it may manifests itself as simple socks and a blaze. More extreme sabinos will have white patches, often with roaned edges, creeping up their sides from the underside of the belly. The most extreme sabinos will look entirely white or nearly so, often retaining a few patches of color along their toplines, particularly on the ears or in the mane.

Dominant White (also called white spotting) is a pattern that was for a long time thought to be part of the sabino gene complex. Like sabino, the amount of white on the coat can vary, though most dominant white horses tend to be heavily patterned or nearly all white. Interestingly, the pattern is usually the result of a spontaneous mutation of the KIT-gene, so loudly marked foals can result from otherwise plain parents. More than 20 white spotting W-mutations have been identified so far in various breed. With some of these mutations, horses that are homozygous for the pattern may be more dramatically marked.

Splash white horses look as if they've literally been splashed with or dipped in white paint from the underside. Splash white is an incomplete dominant. Homozygous spashes will have more white than heterozygous splashes. Splash markings tend to have smooth, crisp edges, and most splashes have blue eyes (especially the homozygous ones).

Most pinto patterns can range from minimal expressions (a nearly solid colored horse) to extreme expression (an all-white or nearly all-white horse). White horses resulting from tovero and sabino patterns are completely viable. White horses that are homozygous for frame overo, however, are known as lethal white overos (LWO). For more information on lethal white, please read my page about white horses.