A white horse has mostly pink skin under its hair coat, and may have brown, blue, or hazel eyes.

Skin color is the most common method for an observer to distinguish between mature white and gray horses.

[2] Depigmentation phenotypes have various genetic causes, and those that have been studied usually map to the EDNRB and KIT genes.

There are 32 identified variants of dominant white as of 2021, plus sabino 1, each corresponding to a spontaneously-white foundation animal and a mutation on the KIT gene.

Researchers have suggested that at least some forms of dominant white result in nonviable embryos in the homozygous state, though others are known to be viable as homozygotes.

While homologous mutations in mice are often linked to anemia and sterility, no such effects have been observed in dominant white horses.

[5] Sabino-white was one of the earliest dominant white alleles discovered, but was not originally recognized as such, hence the different name.

[9] Congenital stationary night blindness is present at birth and is characterized by impaired vision in dark conditions.

Lethal white syndrome is a genetic disorder linked to the Frame overo (O) gene and most closely studied in the American Paint Horse.

Affected foals are carried to term and at birth appear normal, though they have pink-skinned all-white or nearly-white coats and blue eyes.

However, the colon of these foals cannot function due to the absence of nerve cells, and the condition cannot be treated.

Foals with Lethal White Syndrome invariably die of colic within 72 hours, and are usually humanely euthanized.

The lack of pigment in the skin and hair is caused by the absence of pigment-producing cells called melanocytes.

Gray is controlled by a single dominant allele of a gene that regulates specific kinds of stem cells.

In contrast, many albino mammals, such as mice or rabbits, typically have a white hair coat, unpigmented skin and reddish eyes.

For example, the Paso Fino Horse Association registers cremellos and other cream colors as "albino.

In other mammals, the diagnosis of albinism is based on the impairment of tyrosinase production through defects in the Color (C) gene.

[18][25] Most commonly, reptiles with a condition homologous to human OCA1A retain their reddish and orangish hues.

However, other mutations in SLC45A2 are responsible for normal variations in skin, hair, and eye color in humans and .

One of the best-known examples was "Silver," ridden by the Lone Ranger, a role actually played by two different white horses.

For example, Herodotus reported that white horses were held as sacred animals in the Achaemenid court of Xerxes the Great (ruled 486–465 BC),[31] In more than one tradition, a white horse carries patron saints or the world saviour in the end times, including Hinduism, Christianity, and Islam.