The color purple can appear in snakes, although a true, natural purple pigment is non-existent. This coloration is achieved either through an optical effect known as structural color or as the result of selective breeding and specific genetic mutations in captive-bred animals.
How Snakes Produce Color
Snake coloration is determined by specialized pigment cells called chromatophores, which reside in the dermal layer of the skin. The three main types are melanophores (producing black, brown, and gray melanin), xanthophores (yellow to orange pigments), and erythrophores (red pigments).
The colors observed result from how these pigment layers are stacked and interact. For instance, green is created when yellow pigment is layered over light-reflecting cells that scatter blue light. True purple pigment does not exist naturally in reptile skin cells.
The Illusion of Purple: Structural Color in Nature
Purple or blue coloration in natural snakes appears through structural coloration, an optical phenomenon. This effect, often called iridescence, causes the color to change depending on the angle of light and the viewer’s perspective. It is a physical effect, similar to how a soap bubble displays a rainbow.
Structural color is generated by specialized cells called iridophores, which sit deep in the skin layers. Iridophores hold microscopic, crystalline platelets, typically made of guanine, rather than colored pigment. These organized structures scatter and reflect light waves, creating a purple or iridescent sheen when light is scattered in the blue and violet wavelengths.
The Sunbeam Snake (Xenopeltis unicolor) and Rainbow Boas are prime examples. Their dark scales contain iridophores that create a prismatic effect when hit by light, shimmering with colors including deep violet or purple. This vibrant effect is independent of the snake’s underlying chemical pigments.
Genetic Manipulation: Creating Purple Morphs in Captivity
The development of snakes that maintain a purple or lavender hue under ordinary light is an achievement of reptile breeders, known as “morphs.” These colors arise from recessive gene mutations that modify existing pigment-producing cells. These mutations alter the expression of existing red, yellow, and black pigments.
The “Lavender” morph in the Corn Snake (Pantherophis guttatus) illustrates this principle. A genetic change causes melanophores to produce abnormal melanin and dramatically reduces red pigments in the xanthophores. This alteration results in dark areas appearing gray instead of black and red areas becoming a muted pink, leading to an overall dull, purplish-gray or lavender appearance.
Similarly, the “Lavender Albino” Ball Python (Python regius) morph is linked to a mutation in the OCA2 gene. This mutation greatly reduces melanin production. The reduction in the darkening pigment, combined with the remaining red and yellow hues, yields a soft lavender or light purple background color in the adult snake.