Striated Fusilier

Found in schools, feeding midwater over coastal coral reefs. Varies in colour from blue to red with night and day.
Western Indian Ocean - Red Sea to Arabian Sea

Fusiliers are close relatives of snappers, but are much smaller and more slender.
Schools of fusiliers often have other species mixed in.
Although their colour is predominately yellow/blue, at night and when resting their colours change to red/green.