Adult blue streak wrasses usually grow to be 4 inches long (Grant,1978).
Wrasses possess a smooth, compressed, elongate body with a pointed snout. They have small mouths with prominent lips. They have jaws and teeth, particularly 2 canines that are curved anteriorly in each jaw.
Wrasses have a rounded caudal fin along with a dorsal fin consisting of 9 spines and 9-11 rays and an anal fin with 2-3 spines and 9-10 rays (Marshall, 1964). Wrasses have very small scales and the head is normally scaleless.
Blue streak wrasses are brilliant blue with a broad jet-black band that runs from the tip of the snout to the end of the tail, starting out narrow at the anterior end and gradually broadening towards the posterior end. This band usually takes up most of the tail, except the upper and lower rays which are a shade of blue (Marshall, 1966). Young wrasses are sometimes all black, except for a pale streak along the lower, upper and back caudal rays (Marshall, 1964).
The colors of young and adult wrasses differ (Smith, 1965). They are also known to change colors based on mood (Grant, 1978).
There is no geographic variation in morphology or coloration.