Ebony, a black mustang mare adopted by Rhonda Groves
BLACK pigment is one of the two Base Colors. It is created chemically by eumelanin, one of two color pigments that horse hair is capable of producing.

Genetically, Black is determined at the Extension locus on the DNA strand. It is the Dominant form (red is the recessive form) and is notated as "E."

Black horses are typically born a mousey grey or greyish brown color (similar to a mature grullo) which darkens to black upon the first shedding.

	This is in marked contrast to Grey horses, who are born any color or color pattern, which gradually lightens to grey and then white - a process which may take years.
Gus, a grullo mustang, as a weanling and as an adult
Grullos (the Black-based form of Dun), start out yellowish, sort of like buckskin, and mature to a soft grey-brown with dun striping.
	Horses who are born solid black usually change to something else (brown, brindle, grey, roan, etc.) Horses who are born mousey grey-brown usually turn out Black.

 
Freisians are an all-black breed. (DeVore Friesians at Grass Valley Draft Horse Classic)

BROWN: If a black horse or donkey has a light muzzle, lighter coloring around the eyes, elbow and flanks, it is called a Brown.

This filly's faded, sun-bleached winter coat is shedding out to reveal a rich black summer coat. Most black horses will experience some fading over a season. Whether the occasional non-fading black is the result of nutritional, environmental, or genetic actions is not, to the best of my knowledge, known.

Black Base with other genes:

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  Smokey Black (very likely the black horse in the middle is a smokey black) is black with the Creme Gene. It can look like any other black, or sometimes like a faded brown-black, but is genetically capable of producing the entire range of Creme patterns, including cremello and palomino.
   

• Smoky Cream is black with two Creme genes. Smoky Creams look like Perlinos and Cremellos. If you don't have the pedigree, you probably can't tell the difference.
   

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  Grullo is black with Dun gene
   

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  Blue Roan is black with Roan gene
   

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  Bay is Black with Agouti gene aka "Bay Modifier "
   

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  Brown has many causes:  Summer "Sunburned" Faded Black, Dark Bay, Dark Bay or Chestnut with extreme Sootiness, Black with Pangare, Smoky Black (Creme gene) or Silver on Black

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  Black and White Pinto (Tobiano, Frame, Sabino, Splash, Tovero, etc.)