my male xanth randomly shows some darks spots mainly on the top of his back.
when i saw him at the pet store he was very green/yellow and a little bit of blue, looked reallly cool, on the way home and when puting him in his new enclosure he did not have any dark colors or spots anywhere, stayed the same color from when we first boght him.
he started showing dark colors about a month after we got him, i would randomly check on him and he would have dark spots on his back and he wasnt even under his basking light to maybe think he could be hot or somthing. i sure he wasnt cold either.
i think its just the mood they are in, just like us, when we get mad most of us get red.