Chromatophore

Chromatophores are pigment-bearing or light-reflecting cells in the integument of fish. Different types include: melanophores (black/brown melanin), xanthophores (yellow carotenoids/pterins), erythrophores (red/orange), iridophores (reflective guanine crystals), and leucophores (white). Fish can change colour rapidly by dispersing or concentrating pigment granules within melanophores under neural and hormonal control. This serves in camouflage, species recognition, sexual display, and thermoregulation.

Cuttlefish and flatfish are masters of rapid chromatophore-controlled colour change, matching their background almost instantaneously.