University of Massachusetts
Colors and their role in survival
Plants may absorb certain rainbow colors after the evolution of genes necessary for their synthesis because some colors are part of certain vitamin chemistry essential to either or both the plant and/or its herbivore consumer, as pointed out by Jeff Cole. A good example of that is vitamin A derived from the carotene in the roots of carrots and in the endosperm of yellow corn kernels. Vitamin A deficiency results in night blindness and degeneration of skin tissue as occurs in elderly people. Certain colors of solar radiation may have deadly effects on exposed living things. The best example is ultra-violet (U.V.) radiation, which in unprotected white skin causes sunburn and sometimes skin cancer. Protection from U.V. damage is necessary. U.V. resistance may come from purple-violet colors in the target which reflects those colors away so the would be target survives and the radiation is blocked. Here on Earth, life is usually protected from dangerous U.V. radiation by an ozone layer of pale blue gas extending from nine to 18 miles high. In blocking U.V. radiation from the sun, it also tends to maintain seasonal temperatures on Earth. Purple colors in food plants such as cabbage, lettuce and even corn will give the reflective type of U.V. resistance. In people, purple clothes and suntan lotions may prevent or reduce sunburn on the skin. White people seem to object to coloring their skin purple but melanin is equally effective and survival of the fittest has blessed many people with this, especially those from tropical areas. In artic areas, people seem to need the U.V. radiation to photosynthesize vitamin D, giving strong bones to fight a cold rugged environment.
In plants, especially trees, red and yellow color, as seen in the beautiful autumn leaves in the northern United States and Canada, seems to be effective in attracting the red and yellow heat rays of the sun sufficiently to extend the growing season, especially for Maple trees, so that the range of their habitat extends northward so much that its leaves have become a Canadian symbol. In another example, the leaves of corn races adapted to cold high elevations in parts of Mexico and South America have become inherently red, apparently to solve the same heat problem.