Without sunlight, our bodies can not produce vitamin D or reset key brain chemicals vital for health and sanity. So in the real' scientific sense, we are creatures of light. Yoga teaches about light centers of the body, key locations on the spine where nerve centers meet and channel neural energy to the rest of the nerve endings. The constant flow of energy to these pathways is said to produce a specific color frequency that, when visualized can improve health and awareness. Interestingly enough, these colors correspond to the scientific approach to the light spectrum that when split from the original whole' light, creates a rainbow.
Many faiths have stories of rainbows being a message from the heavens.
In Norse mythology it's a rainbow bridge to the heavens. In Greek mythology it's a bridge traveled by Iris to deliver messages from Olympus to earth and the underworld. In the bible it's God's promise to never again destroy man by water. And artists know that the color white contains all the colors of the spectrum. The Native Americans have a word to describe the family of man.