Black (E) is one of the foundation colors. Ponies are black, chestnut, bay, or brown with other colors diluting/modifying the base colors. Extension and agouti form the basis of all equine color. Extension determines whether or not a pony has black or not and agouti determines where it will go. Black horses have the dominant form of extension and the recessive form of agouti.
Many blacks do not look true black due to sunbleaching, which are known as fading blacks. Some blacks don't fade no matter the elements, and are known as non fading blacks. Non fading blacks often have a bluish (aka blue black) sheen to their coat. Blacks can be born as either an obviously black color or as a greyish black color. The best way to determine if a horse is black or not is to look at the muzzle. If the horse is sunbleached but the muzzle is still black it is most likely a black. If the muzzle is brown than the horse is a bay or brown.
Black is known to be a suppressor of white markings and patterns. Black based ponies can have extensive white, however it will be less common than in chestnut based ponies. Minimally marked white will be more common on black based ponies than on chestnut based.
Black is likely an original color in Chincoteagues as it is widespread and the breed was originally all solid dark colors. A 1891 article in the New York City newspaper The Sun stated that the ponies "are most frequently black, gray, sorrel, or dun [buckskin]." Leonard D. Sale wrote in 1896 in The Horse Review of Chicago that, "The prevailing colors are bay, brown, chestnut and light sorrel. A Washington Post article from 1902 stated that the prevailing colors were bay and black. A 1923 St. Petersburg Times article described the ponies as "bay, gray, dun [buckskin], black, and sorrel". A Delmarva Star article describing the 1930 Pony Penning described the ponies as "many colored", with blacks, browns, bright bays, and so many with spotted coats."