It's body will change color, release an ink cloud and jet away to safety. Several blotches of ink can be released before the ink sac is empty. The ink is toxic to an octopus in a confined space such as in a cave with little water current or in captivity. Color change in octopuses is initiated by the eyes. The chromatophores consist of three bags containing different colors which are adjusted individually until the back ground is matched.
Coloration reflects mood, white for fear, red for anger, brown is the usual color.
Many octopuses produce venomous secretions. This venom is fatal to their favorite prey - crabs and lobsters. The tiny Blue Ringed Octopus in Australia is deadly to humans. In some species, the male can be distinguished by modified sucker discs at the tip of one of it's arms. This modified arm is used to remove a packet of sperm from within his mantle cavity and insert it into the mantle cavity of the female.