What crab is this?

[PeterEde]

I have 2 red crabs hiding in the rock but also 3 or 4 of these

 

[blaxsun]

The green one is an emerald crab. Where are the red ones?

 

[PeterEde]

The green one is an emerald crab. Where are the red ones?

I suspected an Emerald of some kind but it does not have the same carapace as the emeralds I can find on google