This is a model of the chromatophores of Sepioteuthis. Different colored chromatophores are controlled by different nerve fibers. This allows the squid to selectively retract or expand sets of chromatophores and increase or decrease the amount of a selected color. For example, by retracting all of the black pigmented cells, the squid will appear to suddenly lighten. By expanding the red chromatophores, as Loligo may do when excited, the animal will flush with a deep red. The sudden retraction of all the chromatophores (as seen in the illustration) has the net effect of reducing all the colors and the squid appears to fade into the water column.

Click here to see a model of an individual chromatophore being retracted and expanded.