Horses have been selectively bred for color or purpose for centuries. The wild Caballine horses of 3000BCE were initially Bay or Black in color.
Around 1500BCE, arguably the oldest selectively bred breed in world began to take shape; Arabian. At that time, the Arabian Horse was most certainly smaller in stature, and most likely came in every color. In the early development of domestic horses, the color matched that of the solid color Iberian Horses and Przewalski’s horse with possible dun factors and very little white markings.
Modern Przewalski’s horse in Binder Park Zoo in Battle Creek Michigan. Dun in color with minimal dun factors. This leg striping and color variations most likely acted as camouflage in the grasslands where the wild horses lived.
By Ltshears – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7412304
Selective breeding then made the move away from those colors with primitive or camouflage markings of the wild horses, into more solid and flashy colors. The colors of Arabians are:
Chestnut – Can be various Red/brown body with matching red/brown mane/tail. Often times the mane/tail will have a mix of blond/red in it, and can be completely Flaxen (blond)
Bay – Red/brown body with Black points. Points include: Mane, Tail, Ear outline, and muzzle.
Black – A horse black in color. A horse with a Dominant black gene will always pass on its color to its foal. You may also see a black/brown looking horse, it may also be black, just not pure black in the sense of genetics.
Grey – A color mutation with occurs when a horse transitions to a white color. Since the skin of the horse is still black, this horse is not true white. They make have brown flecks known as fleabitten, or silver round marks known as dapple color. Mostly born bay or Black, these horses change color at varying points, in their life, and to varying degrees. While you do register your horse as a grey, it’s technically a mutation, and not its own color.
Some time between 1500BC and 1AD, the Sabino gene shows up in the Arabian horse. In 900AD there were reports of “party colored” horses, which is believed to wildly colored horses of Rabino or Sabino coloration.
Rabicano is a concentrated pattern of white hairs similar to roaning. The coloration occurs over black skin, so this is not a pinto spotting. It often is accompanied by white hairs in the top of the tail. True roaning occurs all over the body, not in concentrated areas.
Note the Sabino markings on Lord Grosvenor’s Stallion. The white splashing would have been over top of pink skin. Although these markings are not typical of how you think of pinto spotting, the collective white markings make up the same area as a larger, Tobiano spot. The high white legs, and the under the chin white markings are additional Sabino traits.
A Tobiano is a Pinto coloration where the white spots cross over the back. they typically have white legs, and a darker face.
An Overo is a pinto coloration where the white spots stay on one side of the horse or the other. From the neck and across its back is a solid color. The mane and tail are typically solid, and the face is typically bald.
The Arabian horse does not carry the genes for true Tobiano or full Overo patterns. Even modern day purebred Arabians only carry the Sabino gene.
Arabians were domesticated in the middle eastern area of the Eurasia continent. During this same time period, other groups of homo sapiens were utilizing technology learned from other tribes to corral and domesticate wild horses near their own homeland. Once they had captured generation A, they bred generation B with the qualities that made a good domestic horses. This is not so different from how modern breeders use selective breeding to create what they believe is the perfect type for that specific breed.
Interested in why a horse foals out with one color over another? Or what color your mare might have? Go to this website run by Animal Gentics Inc.
Chestnut Horse: By Original uploader was Karlyne at fr.wikipedia – Transfered from fr.wikipedia, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=4103673
Bay Horse: By evelynbelgium – originally posted to Flickr as IMG_6052, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=6293746
Black horse:By Montanabw – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7296454
Rabicano Horse: By Coreada at the English language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1858292
Grey horse: By Yelkrokoyade, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2492766
T. Jansen, et al., Proc. Natl. Acad. Sci. U.S.A. 99, 10905 (2002). doi:10.1073/pnas.152330099pmid:12130666