Cephalopod skin contains three layers: chromatophores (pigment cells expanded by radial muscles under direct neural control), iridophores (structural color via thin-film interference), and leucophores (broadband reflectors). A single octopus has ~1 million chromatophores, each expandable from 1% to 100% area in ~200ms.
Cuttlefish produce traveling wave patterns (passing cloud) coordinated by central pattern generators in the optic lobes. Lateral inhibition networks similar to Turing's reaction-diffusion create spots and stripes. The high spatial resolution of the skin allows pixel-like control — each chromatophore is individually addressable.
Paradoxically, all tested cephalopods are colorblind — they have a single opsin type. Yet they produce complex chromatic patterns. A leading hypothesis: off-axis pupil shapes create chromatic aberration, allowing wavelength detection through focus differences. Polarized light sensitivity (via iridophores) adds an additional communication channel invisible to predators.