An octopus can change the color of its skin to blend in with its surroundings. Two kinds of skin cells are part of the story. The first kind are chromatophores, which are special pigment cells that let an octopus change color. Tiny muscles around each color sac squeeze it open or let it close, so the color shows more or less. The second kind are iridophores, which are skin cells that make shiny, rainbow-like colors. Octopuses can change color faster than almost any other animal.

The skin can change in other ways too. An octopus can change the texture of its skin, raising bumps called papillae. So the skin can change how an octopus feels to the touch as well as how it looks. The mimic octopus changes how it looks in a bigger way, because it can copy the look and moves of several different animals. Both are more than a change of color.

Looks can also be a message. A blue-ringed octopus is a small octopus with bright blue rings. It flashes the rings as a warning, and people should never touch one. An octopus can also squirt out a cloud of dark ink to help it escape. A warning and an escape are two more jobs for an octopus's body.

Now for a puzzle. You may have heard that octopuses change color because they see the colors around them and copy them. In fact, most octopuses are technically color-blind, yet they can still match the colors around them. An octopus can change the color of its skin to blend in with its surroundings even though it is technically color-blind.

Words to know

• chromatophores: color cells
• iridophores: shiny cells
• papillae: skin bumps
• pigment: coloring matter