How do octopuses change color?

Octopuses change color and texture using a sophisticated system of specialized cells and muscular control. It is essentially a biological display screen.

The process relies on three main components:

1. Chromatophores: These are tiny, pigment-filled sacs located just under the skin. Each sac is surrounded by a ring of radial muscles. When the octopus’s brain sends a signal, these muscles contract, stretching the sac wide and making the color visible. When the muscles relax, the sac shrinks to a tiny, almost invisible dot. By controlling these sacs—which contain colors like yellow, red, and brown—the octopus can create intricate patterns.
2. Iridophores and Leucophores: Beneath the chromatophores are layers of cells that manipulate light. Iridophores contain reflective plates that bounce light back to create metallic blues, greens, and silvers. Leucophores are broadband reflectors that scatter all light hitting them, allowing the octopus to turn bright white or match the ambient light of their surroundings.
3. Papillae: Beyond color, octopuses can change their physical texture. They have small muscular protrusions under their skin called papillae that they can extend or retract to mimic the bumpy surface of a rock or the smooth texture of a piece of coral.

Because these changes are controlled directly by the nervous system, an octopus can shift its appearance in a fraction of a second, allowing it to camouflage itself, communicate with other octopuses, or startle potential predators.