How Octopuses
Change Color

Octopuses put chameleons to shame. An octopus can change its entire appearance—going from red to white, from stripes to spots, from bumpy to smooth—in one-tenth of a second. The secret is its amazing skin, which it changes to blend with its surroundings, startle prey, scare away predators, and signal to mates and rivals.

No one has decoded what all the different colors and shapes mean for all the different octopus species (though in many species, an octopus who turns red is excited, and one who is white is relaxed). But scientists do have a good idea how octopus skin works.

Small muscles in the skin can pull it into the peaks called papillae. For its color palette, the octopus uses three layers of three different types of cells near the skin’s surface. The topmost cells are called chromatophores (cro-MAT-uh-fores). Each chromatophore cell is like a little pot of color enclosed in an elastic sac. When the octopus chooses to change color, it can use its muscles to open and to reveal a lot or a little of each pot—or not. It can make each chromatophore as big as seven times its resting (and invisible) diameter. The chromatophores may contain the colors yellow, red, brown, and black (depending on the species of octopus).

A middle layer of cells, the iridophores (eh-RID-uh-fores), can create an array of glittering blues, greens, and golds. By using iridophores in combination with chromatophores, for instance, the octopus can create colors such as purple and orange. The iridophore cells don’t open and close, but the octopus can change the angle of each cell to reflect light like a tiny mirror.

At the deepest layer of skin are the octopus’s leucophores (LEW-kuh-fores). These, too, reflect light, but instead of glittering colors they can create a white shine.

How does the octopus know which colors to turn? Scientists aren’t sure. Especially because they have determined, by counting the different light-receiving pigments in the octopus eye, that octopuses are colorblind!