Ball pythons and dark/light phases

[M.P.C]

so i keep hearing the terms light and dark phases when people are talking about bigger snakes like retics and boas but never with ball pythons outside of females glowing when gravid.... i just went to check on roland today and he is soooo dark now its like someone swapped him for another snake... is this normal or something to worry about, he is such a relaxed and friendly guy i just want to make sure this is nothing to worry about... i can get pics a little later if needed