Albinism
Albinism, or amelanism, is a genetic condition in which the skin's pigment fails to develop in the typical manner. The skin's color is created by cells called chromatophores. Mammals generally only have one type of chromatophore. If those cells fail to function, then there is no color at all so the mammal appears white. Among reptiles, there are three types of chromatophores, so if a reptile is missing one, it may be technically albino, but not be totally white. The three types of chromatophores in reptiles are melanophores, xanthophores and iridophores.
Color in Albino Reptiles
The melanophores interact with an amino acid called tyrosine to produce melanin. When no tyrosine is produced, no melanin is produced in the reptile's skin, and the reptile has no black or brown pigment. This is known as tyrosinase-negative (or T-) albinism, and it is a common type of albinism in corn snakes, pythons and boas. If tyrosine is produced, but for some reason fails to interact sufficiently with the melanophores, then slight amounts of melanin are still produced, though the reptile is still referred to as albino. This is known as tyrosinase-positive (or T+) albinism.
Albino Kingsnakes
Most albino kingsnakes have T+ albinism, so they still are able to produce slight amounts of dark pigmentation. Typically they appear to have a pale purplish, or lavender, coloration, which is why they are sometimes called lavender kingsnakes. Because the other two types of chromatophores are still working, there is often some pale yellow color in albino kingsnakes in the form of stripes, bands or splotches.
Frequency of Occurance
Few kingsnakes in the wild exhibit albinism. The lack of color means that any natural camouflage is missing, so the young snakes are easy prey for predators, and the adults have a harder time catching a meal. Because of those difficulties, the gene is not typically passed on. In captivity though, the pale lavender color is deemed attractive by many collectors, so kingsnakes with that gene are often selectively bred to increase the albino population.