Horse colors are inherited through genetics of the parents (stud or sire is the male and mare or dam being female). Color has nothing to do with the performance of the horse. Color of a horse can change with age, sun, shade and time of year.
According to “The Horse, Second Edition” by J. Warren Evans, Anthony Borton, Harold Hintz and L. Dale Van Vleck, all horses carry the genetic makeup for either black or chestnut (chesnuts are shades of red or brown. The genetics of the horse decide the degrees of red or brown it will have. When you add white hairs to these base colors, white patterns are produced. There is often confusion between color and pattern like roan, paint or gray.
Horse Colors – Blacks
Genetics for black color can produce the horse colors: black, bay, seal brown, grulla, buckskin and perlino. All blacks have black lower legs, mane and tail or “points” (except for perlino).
A true black horse will not have any red or brown hairs. Seal brown color will have a brown muzzle, behind the shoulder and on the upper back leg. Bays have a mostly red body with the points being black. Black and seal brown are diluted down to grulla. Grulla can range from slate gray to a light brown. Grulla will have a black dorsal stripe, or stripe running down the middle of the back.
Diluted bays and browns are buckskin in color, the body can be a light red or light yellow with black points. If the horse has a dorsal stripe, it is considered a dun rather than a buckskin. Bays can also be diluted down to a perlino color. The skin of a perlino will be pink and the points appear to be more red than black. Perlino is not to be confused with albino.
Horse Colors – Chestnuts
Genetics for chestnut color can produce the horse colors: chestnut, sorrel, red dun, palomino and cremello. Chestnuts will not have black points. Chestnut has varying degrees of red, such as liver chestnut to light red chestnut. Sorrel is considered to be the lightest shade of chestnut.
Above is a chestnut mare.
Above is a dun mare.
Red dun is very light yellow red chestnut with darker legs and a dorsal stripe. Chestnut can be diluted to a light yellow or palomino.
Below is a picture of a buckskin mare (a black) on the left and the same dun mare showing the dorsal stripe on the right.
Above is a palomino mare. Palomino horses can vary in color from dark gold to very pale yellow color or Cremello. Cremello is an even lighter shade of palomino with a white main and tail.
White patterns happen when white hairs appear in the base color of the horse. White patterns are white, roan, gray, tobiano, overo, splashed white, sabino and flaxen.
White horses or dominant white horses are not albinos. White horses are where all the colored hairs are replaced by white hairs, pink skin and colored eyes, sometimes several patches of colored skin.
Above: Gray mare.
Gray horses are not roan, gray is progressive. A foal that will turn gray is born with a colored coat. After the first shedding the gray hairs will appear.
Each shedding will show more and more gray hairs replacing the colored hairs. Gray-white horses will have dark skin and white hair. Usually a horse will gray on the head first, where roan will leave a solid colored head on the horse.
Roan horses do not change with age, but it may appear that there are more white hairs in the winter. The legs and the head are usually solid color and the roan appears on the main body of the horse.Left is a roan gelding.
Above are tobiano spotted horses.
Tobiano spotted pattern is usually a base colored horse with white large spots and the pattern has smooth edges. The white will extend over the back of the horse. The legs are normally white and there is white on the head.
Above is a overo spotted horse with a flaxen mane and tail.
Overo spotted pattern is usually a base colored horse with large white spots and the pattern has irregular edges. The white does not extend over the back. The legs are sometimes streaked with a mixture of colored and white hairs. Bald faces (or all white faces) are common.
Two other spotted patterns are splashed white and sabino they are similar to the tobiano and overo patterns. They are variances of these.
Flaxen is yellow to almost white mane and tail on a colored horse. Flaxen mane and tails occur in only chestnuts, not in blacks. Lighter shades of chestnut will more often have flaxen manes and tails, flaxen manes and tails are rare on darker shades of chestnut.