This seems to be a subject that comes up fairly often.

Pigment cells known as "chromatophores" are responsible for ALL
the coloration that we see in snakes and other animals.

"Melanophores" are pigment cells that under normal circumstances, produce dark pigment(melanin) in the form of blacks,browns and grays.
When an animal(snake) is said to be albino, or "amelanistic" it is usually(with a few exceptions) totally void of ALL dark pigmentation(melanin). When the snake does not exhibit any dark coloration due to this, the snake is left with ONLY any other
underlying pigment(s) it might have, usually leaving the snake's remaining coloration much more vivid looking, and "clean".

"Xanthophores"(xanthos = yellow in greek) are chromatophores that produce yellow and reds.
These pigments are known as "pteridines". These can vary from pure red, to pure yellow, and can be any intermediate shades of these colors as well.
Xanthophores containing a predominately red coloration are known as "erythrophores".....the anerythristic form of "hondurensis" is lacking these reds/yellows, and the word
an-erythristic literally means exhibiting no red.
Xanthophores can also retain yellow to reddish coloration from the snakes diet in the form of "carotenoids". Carotenoid retention continues throughout the snakes life, and the intensity can vary depending on the quantity, and types of carotenoids contained in the diet. Additionally, the animal's
genetic predisposition in the ability to store these will all have an affect on the appearance of the animal.
Most albino "nelsoni", and "hondurensis", as well as many other snakes, start out life fairly white as hatchlings, and become more intensely yellow/red as they age. A good example of a normal wild-type snake that exhibits this is the cornsnake.

This being said,...I apologise for the long drawn-out version, but it's hard to describe this in only a few sentences as to why, and how these things can happen.

These are just some of the things in regards to pigments that is known, and there is much more that is NOT!!

In any case, I hope this helps a few folks understand a few things just a little better.

best regards, ~Doug

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"Better to be silent and thought a fool, than to open mouth and remove any doubt!"