HELP! dogface turned black!

[st3]

my df puffer turned black when i turned on the light to see him tonight then he turned back to normal. what the heck is goin on?

 

[fshhub]

black or gray and dulled in color?, alot of fish turn off color at night, and dull greatly, it seems to be a natural defense against predators, and if the color comes back in minutes(less than a half hour), this IMO would more than likely be the case, but if it stays that color fo rlong, then maybe i would worry, but if it is only minute,s i would not panic