Threespot Chromis

Saw this at Captain Cook. This endemic damselfish is usually dark gray or black with three white spots: one above, one below, and one on the base of the tail. It can lighten or darken the spots, which at times almost disappear. Occasionally it turns almost entirely silver gray. 

Threespot Chromis typically lighten their bodies while leaving their fins dark, a color pattern resembling that of the Hawaiian Dascyllus.