Octopuses and colour

I’m on a break, after finishing filming on Monday night 18/2. 
Currently reading The Soul of an Octopus by Sy Montgomery.
There are lots of interesting facts and observations about octopuses in the book. 
Take this passage from chapter 2: 

“The ability of the octopuses and their kin to camouflage themselves is unmatched in both speed and diversity. Octopuses and their relatives put chameleons to shame. Most animals gifted with the ability to camouflage can assume only a tiny handful of fixed patterns. The cephalopods have a command of 30 to 50 different patterns per individual animal. They can change color, pattern, and texture in 7/10 of a second. On a Pacific coral reef, a research once counted an octopus changing 177 times in a single hour. 
[...] For its color palette, the octopus uses 3 layers of 3 different types of cells near the skin’s surface—all controlled in different ways. The deepest layer, containing the white leucophores, passively reflects background light. This process appears to involve no muscles or nerves. The middle layer contains the tiny iridophores, each 100 microns across. These also reflect light, including polarized right (which humans can’t see, but a number of octopuses’ predators, including birds, do). The iridophores create an array of glittering greens, blues, golds, and pinks. Some of these little organs seem to be passive, but other iridophores appear to be controlled by the nervous system. They are associated with the neurotransmitter acetylcholine, the 1st neurotransmitter to be identified in any animal. Acetylcholine helps with contraction of muscles; in humans, it is also important in memory, learning, and REM sleep. In octopuses, more of it “turns on” the greens and blues; less creates pinks and golds. The topmost layer of the octopus’s skin contains chromatophores, tiny sacks of yellow, red, brown, and black pigment, each in an elastic container that can be opened or closed to reveal more or less color. Camouflaging the eye alone—with a variety of patterns including a bar, a bandit’s mask, and a starburst pattern—can involve as many as 5 million chromatophores. Each chromatophore is regulated via an array of nerves and muscles, all under the octopus’s voluntary control. 
To blend with its surroundings, or to confuse predators or prey, an octopus can produce spots, stripes, and blotches of color anywhere on its body except its suckers and the lining of its funnel and mantle openings. […] And of course the octopus can also voluntarily control its skin texture—raising and lowering fleshy projections called papillae—as well as change its overall shape and posture.” 

Later in the same chapter: 

“… the octopus eye and our own are strikingly similar. Both have lens-based focusing, with transparent corneas, irises that regulate light, and retinas in the back of the eye to convert light to neural signals that can be processed in the brain. Yet there are also differences. The octopus eye, unlike our own, can detect polarized light. It has no blind spot. (Our optic nerve attaches to the back of the eye at the retina, creating the blind spot. The octopus’s optic nerve circles around the outside of the retina). Our eyes are binocular, directed forward for seeing what’s ahead of us, our usual direction of travel. The octopus’s wide-angle eyes are adapted to panoramic vision. And each eye can swivel independently, like a chameleon’s. Our visual acuity can extend beyond the horizon; an octopus can see only about 8 feet away. 
There is another important difference as well. Human eyes have 3 visual pigments, allowing us to see color. Octopuses have only one—which would make these masters of camouflage, commanding a glittering rainbow of colors, technically color-blind.” 

Isn’t that fascinating? It’s like reading about whales in Moby Dick. 
Like Ishmael in Moby Dick, Sy Montgomery has such an immense curiosity and sense of wonder that you feel captivated and feel changed as a person as you read the book—you start to wonder, what is it like to be an octopus? do they have consciousness? do they think? how do they feel about us? how do they see the world? do they dream? why are they so smart? 
Love this book.