Both of the fish in this pixture are Sergeant Majors… so named for the 5 black bars on their body.
Their normal coloring is that of the one in the background… mostly white, yellow and silver.
It is my understanding that it is the males that turn the darker blue color… and they do that when they are guarding their eggs.
If you look closely at the upper right part of this frame… you will notice what looks like a purple stain on the coral head. Those are the eggs.
Sergeant Majors are always an aggressive and a territorial little fish (4-6in long).
But when they are guarding eggs that aggression ramps up a lot… and they don’t want anything, even something as big as a diver, anywhere close to their egg patch.



