Siganus unimaculatus aka one spot foxface.

[darkart82]

Why do these guys changes colors? Is it to warn you before you get stung? Are they stressed? I bought a baby and he is about 2". When he is eating dried seaweed he looks like the stuff he is eating. Other times he just looks normal.

 

[Jdbrine]

They just do it when they are nervous or stressed. When they darken it's also to help the cammo to hide when scared or stressed.

 

[darkart82]

If from a distance he shows yellow, I get up close he changes colors, its kinda cool.