Hypoplectrus indigo has a deep body and head which is highly laterally compressed with a straight forehead and a rather short snout and a protrusible upper jaw.

It has an angular preoperculum which has serrations on its edge and a number of small forward pointing spines on its lower margin close to the angle.

It also occurs along the mainland coasts of Central and South America from Mexico to Mamitupo in Panama and among the offshore islands of Venezuela.

The species in the genus Hypoplectrus are synchronous hermaphrodites and they have the ability to move between "male" and "female" roles when spawning.

However, neither of the Chromis species really resembles H. indigo with its darker blue-black bars and other workers are not convinced by this hypothesis.