The green iguana has a ‘third-eye’ called a parietial eye, in the middle of its forehead. This does not function in the same way as its two side eyes, but enables it to detect movement, especially from above, to help it avoid predators. Their eye color also begins to vary. Iguanas have a remarkable ability to change their color to suit their moods and camouflage needs - so don't be disappointed if the iguana sold to you as a "rare" color, changes back to a more common shade. What the iguanas have been eating may also influence their color.