Nemanthias bicolor

Nemanthias bicolor has a relatively elongated, laterally compressed body which has a standard length which is around three times its depth. It has a moderately large, oblique, terminal mouth, although in males the thickening of the upper lip causes it to be slightly inferior. The maxilla is level with the rear edge of the eye. The dorsal fin has 10 spines and 16-18 soft rays while the anal fin contains 3 spines and 7-8 soft rays. The colouration of this species is sexually dimorphic, the males are more intensely coloured having a violet body with a yellow back, the yellow colour continuing on to the upper lobe of the caudal fin and the dorsal fin has a purple margin.. The females are normally lavender in colour and have a yellow back and caudal fin. The males also have two yellow-tipped filaments at the origin of the dorsal fin which they use when displaying. The maximum total length recorded is 13 centimetres (5.1 in).

Nemanthias bicolor has a wide Indo-Pacific distribution from Réunion and Mauritius in the west to Hawaii and the Line Islands, north as far as the Ryukyus south of Japan and south to northeastern Australia.