Pseudanthias ventralis has males which are metallic purple with a yellow head and a yellow tinge on the back just below the dorsal fin, although sometimes this is masked by heavy purple spotting. The populations from the southern quadrant of their range normally has distinct and circular purple spots in this part of the back. The dorsal fin is red on the spiny part and hyaline or yellowish on the soft-rayed part. The caudal fin is mostly clear and the only markings are two vertical purple lines. The anal fin is clear with an obvious purple line demarcating a are of deeper colouration which contains the anal fin spines and the first soft rays fin. The females are a similar metallic purple colour as the males, but do not have the dame markings. They do have a yellow dorsal fin, the colour just extending on to a small area of the back as far as the caudal peduncle. They also have a red arcing stripe which separates the yellow and purple on the back near the tail. Specimens from other geographical regions show differences in colouration to the above which represents the population from the type locality.[3] The dorsal fin has 10 spines and 17 soft rays while the anal fin has 3 spines and 8 soft rays. This species attains a maximum total length of 7