At my LFS they are labelled "electric blue hermits" The thing that threw me off was the size of their claws. I have to admit though, they are probably the best looking hermits!
they are also called giant blue leg hermit crabs- right now they are just the size of an adult blue leg- but yes they are much coler looking than the rest
they feed jsut as the others do- they just get larger- these are not destructive - other than the potential coral knock over of snail killing for a larger shell- and they are not the same as the zebra hermits