The retinas in the eyes have receptors for color called cones (also known as cone cells). You have on that measures the amount of red light, another measures green light, and the third measures light intensity. Your Occipital lobes in your brain actually process this information as color by reducing the amount of blue light from the other three factors.The cone cells measure red light,green light or blue light. Other cell called Rod cells measures intensity. Humans have full tricolor vision, not bicolor. Most other mammals have only bicolor vision. Cone cells measures Yellow light or Blue light. Rod cells measures intensity. Birds have Quadcolor vision: Cone cells measures Red light, Green light, Blue light or Ultraviolet light. Rod cells measures intensity.