At that size, I can't give you anything better than probably a Central American cichlid or northern South American acara, nd it could be any number of species. I won't rule out a flowerhorn either. Was there any other information given about the little guy?
I like the pretty blue all over...I'm guessing it's a female by the rounded dorsal & anal fins...doesn't mean she's not up for a fight! Cichlids females often know how to rumble, lol. They may be smaller but can be quite sassy. No guess as to species