Emerald crabs are small, usually one half inch to 2 inches for the carapace width. Emerald crabs are usually deeper green when they are younger and eating more greens. The green fades to grey as they age and begin to scavange more. Emerald crabs have "shovel-like" claws as opposed to the sharp pointy claws of more predatory crabs. and if you look were the claw bends you'll see a red spot, thats a true Emerald crab.