Ditto. I was going to suggest the same. The flash can severely wash out color and give a false sense of the snake being much lighter or more yellow. Natural light with no flash is best. Or, try to take on a solid back, or solid white background.
I am a believer than a heterozygous gene can make animals carrying them seem to stand out differently than true "normals" that lack any other genes. But I do not believe that it's a tell-all.