Page 112 - Design in Nature

Under the skin of the cuttlefish is arrayed a dense
layer of elastic pigment sacs called
chromatophores. By using this layer, they can
change the apparent colour of their skin, which
not only helps in camouflage but also acts as a
way to communicate. For instance, a male fish
can take on a different colour when mating than
that it would take on when in a fight with a
challenger.
When a male flirts with a female, it takes on a
bluish colour. If another male comes by during
this, it gives a reddish colour to the half that
faces the other male. Red is the warning colour
used during a challenge or an aggressive action.