I'm just not a big fan of hamlets - their colors really fade in captivity. The shy hamlet is a mimic of a rock beauty - in fact most hamlets mimic other fish, but it isn't always easy to determine who the model is. I've heard that is because they mimic only to the point of confusing crustaceans, and shrimp and crab see things so differently, that to humans, the mimic doesn't look very convincing. I caught a H. gummigutta once, this may be another rock beauty mimic - it faded to a somber brown color. The gemma hamlet mimics blue chromis (if I recall). A bunch of the others mimic different damsels.
Now - that all said, I haven't kept one in over 20 years, so it may well be that better water quality in tanks now days will allow these fish to keep their colors better.
Jay