Pictorial progression on the life of a green tree python.

I don't know anything about snakes but why did it start out as red anyway? I mean it could have started out as green right?. I assume it won't go back to being red since it is a green tree python. Just wondering what the purpose of changing color over this long period of time serves. It could be camouflage but still the question remains - why do they start out red? By the way, nice snake... I also like green.