The modern English word green comes from the Middle English and Anglo-Saxon word grene, from the same Germanic root as the words "grass" and "grow". It is the color of living grass and leaves and as a result is the color most associated with springtime, growth and nature. By far the largest contributor to green in nature is chlorophyll, the chemical by which plants photosynthesize and convert sunlight into chemical energy. Many creatures have adapted to their green environments by taking on a green hue themselves as camouflage. Several minerals have a green color, including the emerald, which is colored green by its chromium content.

What, in nature, is most likely to make things green?