I found this Caribbean Reef Octopus at night on a shore dive in Cozumel, Mexico off the Coral Princess Hotel. The blue-green color shade is pretty common in this species, especially when it is out of its hole.
I like the single tentacle in the image
F22, 1/90, ASA 100, 105mm lens, strobes on 1/2 power


More images of this species at the Caribbean Reef Octopus Gallery at DSI
Enjoy,
M