EMPEROR HELP please

[daviscanbefound]

i have a 12 inch emperor in a 125g.....recently ive noticed that if i have the light on (the same lighting for more than a year) that he goes really light .....from black to almost white with a purplish tint......if i shut the light off and leave it off he goes back to black......any ideas as to y this would start happeneing???

 

[tscharf]

could be just trying to blend in... some animals do this, kinda like camouflage.... its lighter in the tank, so hes lighter.... its darker in the tank, so hes darker

 

[Thalan]

Has anything changed in the tank recently, simple things could spook him and make his survival instincts kick in