I'd say it is a juvenile creole wrasse (Clepticus parrae) from the Caribbean. They reach about 12" in the wild and prefer to swim in schools. The creole fish Paranthias sp. is different.
The one in the picture looks pretty faded...stress or overexposure of the flash? I wouldn't buy just one - they are delicate and unless you have a group of them and handle them like delicate anthias, the long term success probably isn't all that good.
