Charlie is normally a pale yellowish-brown with darker brown markings on his back. Sometimes though, he is completely black -- or as close to it as he can get. His temps seem right, he's basking at 101 F and his cool side is 75. He's 6 inches under a T8 bulb that is only a couple months old. He does have a hide available but almost never uses it. Am I doing something wrong? The dark coloring comes and goes throughout the day and he doesn't seem distressed, eats regularly (veggies and dubias). Should I be concerned?
If it's his whole body changing like that, and it comes and goes throughout the day, it's likely just him adjusting to bask and absorb heat/UVB or to reflect it or anywhere in between. If the dark color is focused around his beard and chest, then it could indicate distress or mood. I don't think it's anything in your setup that is causing an issue.