We have a sub-adult orange shoulder tang (still yellow but with a gray mouth) today as I was watching the tank I noticed he was being pretty shy and hiding in the rock work. When he would poke out, I noticed his face was completely black, almost like a fox face. But then it would go away and he would be back to his normal color. I'm pretty sure I'm not on drugs. I wasn't away that tangs could shift colors or camouflage like rabbit fish do. Does anyone have an sort of explanation for this?