A lunar-tailed bigeye (Priacanthus hamrur), a nocturnally-active fish, off the coast of a lagoonal island. This bigeye is also seen in uniform deep red coloration and, as is true for other bigeyes in the Pacific and Atlantic, can rapidly shift colors and patterns. (Pig Island, Madang)
Fishes that are primarily active at night — such as squirrelfishes, bigeyes, and this soldierfish (Myripristis sp.) — typically have reddish coloration and large eyes. The large eyes effectively act as a light-gathering device, wheras the red coloration is typical because it's metabolically cheap to produce and essentially functions the same as black shading at night (or at great depth). (Mandarinfish Reef, Kimbe Bay)