Wait. Allow me to correct myself. Iridescence is when the various wavelengths of light are not altered, but instead reflected back at different angles. What I'm saying about the blue is let's say, green light hits pigments in the skin and the wavelength itself is what gets altered, not the angle of reflection. Temperature of the snake can have an influence on how much the wavelength gets altered. I think this is why my snakes never appear blue when they are cold.