Skewbald (pinto)Bay (classic)LeopardBlack (true)Piebald (pinto)Blanket with spotsChestnutPalominoDark bay or seal brownWhite (true)Buckskin Gray* Drag / drop or click on the choices above to move them to the answer list.
Quiz Answer Key and Fun Facts
1. Black (true)
The (true) black horse is entirely black over the entire body, mane, and tail (though there may be white markings, such as a star on the forehead). The eyes are brown and the skin is black.
Black is one of the three base coats of horse color, along with bay and chestnut, that are governed by two sets of genes, extension ("E", which governs the production of black pigment) and agouti ("A", which modifies the pigment distribution). If the extension gene is dominant (EE or Ee) and the agouti gene is recessive (aa), then the base coat, mane, and tail will be black, black, black -- no red.
True black should not be confused with dark bay or seal brown (see #4), which can be pretty dark but they are genetically different. (Some consider seal brown to be a fourth base coat, but this is disputed).
True black is not exactly common, especially among Thoroughbreds, but neither is it rare. Black Gold was a black colt who won the 50th Kentucky Derby in 1924.
2. Bay (classic)
A (classic) bay is a horse with a reddish-brown body and a black mane, black tail, and black legs, called black points. When a horseman says "bay", he means "standard bay" or "classic bay".
Bay is one of three base coat colors directly determined by the extension (E) and agouti (A) genes -- the others being chestnut and black. Bay is the base coat produced when the extension (black) gene is dominant (EE or Ee) and the agouti (modification) gene is dominant as well (Aa or AA).
A "bay dun" is a bay horse with dark stripe down the center of the back, darker than the base coat, which is typically lighter than a standard bay's. The legs may also be striped. These are considered primitive markings, and they are caused by dominant dun genes (DD or Dd). A standard bay would have a recessive dun genotype (dd).
Bay is the most common color among many horse breeds, including Thoroughbred horses. Big Brown, who won the 134th Kentucky Derby in 2008, and Mine that Bird, who won the 135th Derby in 2009, are bay horses. Northern Dancer, winner of the 90th Kentucky Derby in 1964 and perhaps the world's most successful sire, was also bay, as was Seabiscuit.
This is one of the most common horse colors and is found in almost every breed. A chestnut horse has no truly black hairs; consequently, the body color is red and the color of the mane and tail may range from flaxen (blonde) to red to brown, but never black.
The base color of a chestnut horse is produced by recessive extension genes (ee). The skin pigment is black, but the hair appears red. The agouti genes have no effect on recessive extension (ee), so whether it's AA, Aa, or aa is irrelevant.
There are a couple of common variations of chestnut; they both have the same recessive expression (ee) genes as an ordinary chestnut:
"Sorrel" is a more ambiguous term that means different things in different regions. In some places it means that the mane and tail are lighter than the base coat, and in others it refers to a lighter chestnut coat.
"Liver chestnut" (or "dark chestnut") has a darker base coat with a brown mane, tail, and legs, and no black points. Liver chestnut is not a separate genetic color; in fact, it is not quite understood why some genetically chestnut horses end up with more deeply shaded coats. Liver chestnut coloring appears frequently in Justin Morgan horses, though it appears to be a recessive trait.
The Triple Crown champion Secretariat was a chestnut horse.
4. Dark bay or seal brown
This color is also called "mahogany bay" or, confusingly, "black bay", or just plain "brown". The seal brown / dark bay horse has black points (mane, tail, legs) but a darker and less red-looking body coat than the classic bay horse.
Some classify this to be a fourth base coat along with black, bay, and chestnut; others consider it a subset of bay. The dark bay / seal brown horse has the same expression genes (EE or Ee) and agouti genes (AA or Aa) as the (classic) bay, which is why many scientists consider this NOT to be a separate base coat. The genetic mechanism for these brown colorings is not completely understood and under dispute.
As a dark bay and a seal brown are practically indistinguishable, some sources and registries do not make a distinction; some even use simply "brown". The Jockey Club (the US-Canadian registry for Thoroughbreds) uses "dark bay or brown". Those that do differentiate contend that "seal brown" horses have tan markings around the eyes and possibly the muzzle; without these markings, it's a "dark bay" in this scheme.
A color that is often conflated with dark bay / seal brown is "liver chestnut" (see question #3). You can distinguish liver chestnut from the dark bay / seal brown, however, because it lacks black points. It has the same recessive expression (ee) genes of an ordinary chestnut.
Cigar, who won the 1995 Breeders' Cup Classic, and who once held the record for the most money earned by a horse, was considered a dark bay Thoroughbred. The champion filly Ruffian was a very dark bay racehorse that was often mistaken for black.
A buckskin horse has a cream or tan body with a black mane and tail, and often black points on the legs as well.
In addition to the extension (E) and agouti (A) genes which produce the base coat, there is the cream gene (Cr) to consider, which dilutes the base coat. Thus it is called a dilution gene or a hypomelanism gene.
This is not a gene with a dominant and recessive form; it is either present or absent. There are three possibilities:
NN (no cream gene)
When a bay horse is heterozygous with the cream gene (NCr), the red in the base coat is diluted to yellow or gold, but it does not dilute the black hairs. This is a buckskin horse (pictured). If the cream gene is homozygous (CrCr), this is called "double dilution", and both the red and black hairs are affected. The horse's coloring will be "perlino", which means the red hairs become cream or ivory, the black hairs reddish or rusty-cream, and the skin rosy-pink.
If there is no cream gene (NN), there is no dilution.
Let's start with a chestnut horse (Remember, the extension genotype is ee). When the cream gene is heterozygous (NCr), the color of the chestnut horse's base coast is diluted to gold or cream. This is called palomino, and it is a "single dilute". The golden base coat is typically darker than the mane and tail.
If the cream gene is homozygous (CrCr), our horse's coat color will be "doubly diluted" to cremello, or sometimes called "cream", with a lighter base coat, mane, and tail and rosy-pink skin, and possibly with blue eyes.
At times, cremellos and perlinos can be difficult to distinguish visually and may require a genetic test if the owner really needs to know the color of such a horse.
Sometimes a cremello looks so fair that a horseman may call it "white", but even if it has blue eyes it is not truly white, a color which is governed by a different set of genes (see #7). Dilution genes have nothing to do with the white patches of pinto coloring either (see #9 and #10). The American Quarter Horse Association until 1999 incorrectly referred to both cremellos and perlinos as "albinos".
7. White (true)
A true white or "dominant white" horse has pink or, more accurately, unpigmented skin, all-white hair, and usually a white nose (or pink). A set of multiple W genes (W1-W32) produces the white color. It overrides the base coat genes (E or A).
Sometimes gray horses that become de-pigmented with age are called "white" horses, but true white or dominant white horses are born white and stay white throughout their lives.
Bear in mind that there are no "albino" horses as such. The whiteness in horse is caused by a lack of melanocytes, whereas albinos have a normal distribution of melanocytes, but they just don't work properly. Melanocytes are the cells that produce melanin, a pigment made from the amino acid tyrosine. A dominant white horse may have brown, blue, or hazel eyes, not the pink eyes of an albino rabbit.
The horse named Silver, the Lone Ranger's horse, was played by two different (true) white horses in the original TV series of the 1950s.
Another gene to consider in a horse's coat is the gray gene (G). If dominant (GG or Gg), the horse will be gray, no matter what other coat color genes may be present.
Some, though not all, grays as they age become "dapple gray", as the horse pictured here. (Right-click chart to view larger image; the dapples show up better.) Essentially, dark rings with lighter hairs inside scatter over the animal's body. This is an intermediate stage in the progressive lightening of grays with age, after which they will start to look mostly white all over, save perhaps for the flanks and and lower legs, and perhaps the face. Eventually all the hair may become completely de-pigmented though the underlying skin remains black; the horse may also develop a "fleabitten" coat, which is white hair dotted with flecks or freckles of a darker color.
A de-pigmented gray horse can be differentiated from the true white horse in that the gray horse will still have black skin, while the the white horse will have pink or unpigmented skin.
Melanoma is fairly common in older gray horses (8 years and beyond). More than 80% of gray horses will have at least one melanoma during their lives. They will begin as benign, but they can turn malignant.
Winning Colors, the third filly to win the Kentucky Derby, had a gray coat. Native Dancer, whose only career loss was the 1953 Kentucky Derby, was nicknamed the Gray Ghost.
9. Piebald (pinto)
A pinto is a horse with patches of white and another color. Piebald is a term for a pinto with black-and-white coloring probably used more in British English than in American English.
The pinto pictured here has what is called a tobiano pattern, caused by the dominant tobiano genes (TOTO or TOto). The tobiano is the most prevalent pattern among pinto horses. The markings are rounded and smooth, they cross the backbone, and the distribution between white and color is 50-50 or thereabouts.
"Pinto" is not a breed but a description; sometimes "paint" with a lower-case 'p' is used synonymously. The American Paint Horse (capital 'P') is a specific breed of pinto horse that demonstrates either American Quarter Horse or Thoroughbred bloodlines (or both).
10. Skewbald (pinto)
A pinto horse that displays white plus any other color besides black is skewbald. Like piebald, "skewbald" tends to be used more in Britain than in America. This horse is displaying the tobiano pattern (genotype TOTO or TOto), but it is also displaying what is known as the "medicine hat" pattern on its head. The top of the head, the ears and the poll (the space between and around the ears) are darker, looking rather like a cap on the head. Ideally, the face would be all white and more of the body would white. The medicine hat pattern was, and remains, highly prized among many of the Native American peoples of the American West.
Both piebald and skewbald pintos are more likely than solid dark-colored horses to develop melanoma. Worse, melanomas that arise in horses that are NOT grays tend to be more dangerous.
A leopard horse or leopard-spotted horse is a white horse with dark spots scattered over the entire body.
Leopard patterns are commonly found in the Appaloosa horse, a North American horse breed, and in the Knabstrupper horse, a Danish breed. There are artistic depictions of leopard horses from Ancient Greece and Han-dynasty China, as well as prehistoric cave-paintings in northern Europe. The leopard gene is believed to be very old, and possibly provided camouflage for equines during the Ice Age.
The opposite of leopard is snowflake, a dark base coat with white flecks (see #12).
Leopard spotting is controlled by the leopard-complex genes (Lp). Appaloosas that are recessive for this gene, and therefore do not display any spotting, may be called "non-characteristic" by breeders. Leopard-spotted coats are also found in the Colorado Ranger, the Falabella, the South German Coldblood, and the Mongolian Altai.
12. Blanket with spots
A blanket is a solid white area usually over the hip area with a contrasting base color, though it may appear elsewhere besides the hip. A blanket may or may not have spots within the white; such spots are usually the same color as the base coat. If the blanket is solid (no spots), it is often called a snowcap.
The horse pictured here displays a blanket with spots. In the non-blanketed areas, there is a snowflake pattern of white flecks over a dark coat (the opposite of leopard, which is dark flecks over a white coat).
The blanket coloring is also controlled by leopard-complex genes, and it is a common coloring of the Appaloosa horse.