The human eye (retina) has three different types of cones that are sensitive to three different ranges of light wavelengths, representing the three primary colors. When there are many photon wavelengths available the eye sees a mixture of primary colors (producing secondary colors) and can perceive all the shades and tints that a TV can produce. Originally, being able to sense colors had survival value. Safe plants to eat could likely be distinguished better in daylight with color than at night in black and white under the moon. Many creatures such as snakes and spiders use color to warn that they are dangerous with venom. Today food is wrapped in livid color to entice us to buy it. Some things never change?