Cold sores - painful sores on the lips and around the mouth, caused by a virus. Canker sores - painful sores in the mouth, caused by bacteria or viruses. Thrush - a yeast infection that causes white patches in your mouth. Leukoplakia - white patches of excess cell growth on the cheeks, gums or tongue, common in smokers.
Metabolism is a combination of chemical reactions that are spontaneous and release energy and chemical reactions that are non-spontaneous and require energy in order to proceed. Living organisms must take in energy via food, nutrients, or sunlight in order to carry out cellular processes.
Anyway, the likely reason that green is important is that plant life was a very large part of what we needed to look at for a very long time, and the same for the ancestors of humanity. If you live in a suburb it might be hard to notice, but the natural world is almost entirely green when viewed from a distance.