In a cloaking clip from the PBS documentary Octopus: Making Contact, a sleeping octopus began changing colors as she seemingly dreamed as she lay upside down in the water. As this was happening, marine biologist Dr. David Scheel amusingly narrated what the dream might be in accordance with the particular shade of camouflage being exhibited at each moment.
So here she’s asleep, she sees a crab and her color starts to change a little bit. Then she turns all dark. Octopuses will do that when they leave the bottom. This is a camouflage, like she’s just subdued a crab and now she’s going to sit there and eat it and she doesn’t want anyone to notice her. …This really is fascinating. But yeah, if she’s dreaming that’s the dream.