i just bought a emerald crab from my lfs and am baffled because this one is purple it is almost adult size and is the color of coraline algae but is not coraline algae build up on its exo skeliton it is truly purple i cant find any id any where on line please help i want to know if this was a rare find or if i have an un id species of crab i personaly have never herd of such a color varity of this crab in my 18 years of exp. Thanks