Palomino is a coat color, not a breed. A palomino horse has a gold body ranging from pale cream to rich dark gold, with a white or cream mane and tail. The color is produced by a single copy of the cream dilution gene (Ccr) acting on a chestnut (ee) base coat. Two copies of the cream gene on chestnut produce a cremello, not a palomino.
Genetics
The cream gene is an incomplete dominant. One copy on chestnut yields palomino. One copy on bay yields buckskin. One copy on black yields smoky black, which often looks identical to black and requires DNA testing to distinguish. Palomino cannot result from a bay or black base; the base coat must be chestnut (red-factor homozygous: ee at the Extension locus). For a full map of how base colors and dilutions interact, see Horse Coat Color Genetics.
Because the cream gene behaves as incomplete dominant, two palominos crossed together produce approximately 25% cremello, 50% palomino, and 25% chestnut offspring on average. There is no guarantee of color in any given foal.
Breed Standards
Palomino appears across many breeds: American Quarter Horse, Tennessee Walking Horse, Morgan, Arabian, and others carry the color. The Palomino Horse Breeders of America (PHBA), founded in 1941, maintains a color registry open to horses that meet its color standard regardless of breed. The PHBA standard requires a coat the color of a United States gold coin, with a mane and tail no more than 15 percent dark hair.
Some breed registries exclude palomino. The Thoroughbred registry does not recognize the color because the cream gene is not present in the Thoroughbred gene pool.