Three blue damsels from the Pomacentrus genus are very common in the aquarium trade and all have very similar common names that may even be interchanged in some references, including "Electric Blue Damsel" or "Neon Blue Damsel". These three damsels are the Allen's Damsel (P. alleni), the Yellow Belly Damsel (P. auriventris) and the Neon Damsel (P. coelestis). A few other less common damsels also resemble these three.
The Yellow Belly Damsel (P. auriventris) is metallic blue and may sometimes be iridescent as well. The bottom half of the fish and the tail is bright yellow or gold, usually forming a sharp L-shaped color change towards the rear of the fish.