Octopuses have no hard shell or outside armor, so they had to evolve ways of not being seen. One of those ways is the skin. An octopus can change the color of its skin to blend in with its surroundings, and it can change color faster than almost any other animal. Its skin has special pigment cells called chromatophores that let it change color. Tiny muscles around each color sac squeeze it open or let it close, so the color shows more or less.

The skin is built in layers. An octopus's skin has three layers of chromatophores, and the pigment in each layer reflects a different color. An octopus can have from tens of thousands to millions of chromatophores, each controlled by signals from the brain. Chromatophores are not the only color cells. Iridophores add shiny, rainbow-like colors to the mix.

Some looks are made to be noticed. The blue rings of a blue-ringed octopus are an example of aposematism, bright colors used as a warning. A blue-ringed octopus is a small octopus with bright blue rings, and people should never touch one. The mimic octopus does something different. As of November 2026, it can successfully impersonate at least 16 very different animals, according to Guinness World Records. It can copy the look and moves of several different animals.

The eyes are a surprise. An octopus eye is built much like a human eye, but it has no blind spot because its optic nerve passes behind the retina. Octopus eyes have only one type of photoreceptor, which means they can detect differences in brightness but not color in the usual way. You may have heard that octopuses copy the colors they see. In fact, most octopuses are technically color-blind, yet they can still match the colors around them.

Words to know

• chromatophores: color cells
• aposematism: warning colors
• photoreceptor: light-sensing cell
• iridophores: shiny cells
• armor: hard body cover