Regal Tang color switcH?

[monza]

My regal tang that I have had for years, had a wild color switch tonight, ever seen this before??

His entire upper body normally black went a super bright yellow color for about ten minutes then switched back to his normal colorings? No change in his environment.

What’s up with that anyone seen that before? I freaked as did my house guesst freaked as I exploded from my seat for my camera trying t get a picture, I missed the pic, the fish returned to his normal color?