thanks, I think more and more emerald, since I read that a lot of them are nearly brown, not really green.

Same family anyway.

Fishy time hit it on the head with mithrax family crab , what is sold as an emerald crab is probably a couple of different species of the same family of crab that happen to be green .

Might be here
http://www.ultimatereef.net/info/iddb/crabs.php