Leucism
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Leucism is a wide variety of conditions that result in partial loss of pigmentation in an animal—causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles, but not the eyes. It is occasionally spelled leukism. Some genetic conditions that result in a "leucistic" appearance include piebaldism, Waardenburg syndrome, vitiligo, Chédiak–Higashi syndrome, flavism, isabellinism, xanthochromism, axanthism, amelanism, and melanophilin mutations. Pale patches of skin, feathers, or fur can also result from injury.
Leucistic white lions owe their colouring to a recessive allele. Note the eyes and lips remain the normal colour. Studies have shown that the reduced pigment comes from a mutation in the gene for tyrosinase, the same as causes Type I oculocutaneous albinism in humans.
This white horse owes its coloring to a dominant allele (dominant white).
A leucistic rock dove. Both the eyes and legs are still of the normal colour.
Leucistic Texas rat snake (Pantherophis obsoletus)
Chromatophore
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Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, have a class of cells called melanocytes for coloration.
Chromatophores in the skin of a squid
A veiled chameleon, Chamaeleo calyptratus. Structural green and blue colours are generated by overlaying chromatophore types to reflect filtered light.
The purple-striped dottyback, Pseudochromis diadema, generates its violet stripe with an unusual type of chromatophore.
Zebrafish chromatophores mediate background adaptation on exposure to dark (top) and light environments (bottom).