Thanks for the feedback!
Well I think I have a good idea which species of Mantis I've got. BEELZEBOB suggested
Gonodactylus smithii, which is actually the same species he has. But I was skeptical as the description identifies this as an Indonesian/Philippine species and I confirmed with my LFS that the rock he was on came from Florida. I think what I've got is a
Neogonodactylus wennerae. It's supposed to be a common hitchhiker on Florida live rock and has some characteristics consistent with my little guy. That purple color on the bottom image is almost identical to the shade my guy appears right now. The yellow-orange antennae and small metallic blue spots are also consistent with my Mantis' appearance.
He's still very very small and will likely change quite a bit before he gets big enough to be certain. But right now he fits that description better than any of the others.