Leaves appear green because of the chlorophyll they contain. Chlorophyll is the part of the leaf that uses carbon dioxide, sunlight and water to produce sugar. A leaf with plenty of chlorophyll masks other pigment colors.
A pigment is a substance that absorbs, reflects and transmits visible light, which consists of colors that the human eye can see. When white light illuminates a pigment, the color that a person sees on leaves is the color of light that the pigment reflects and/or transmits. The pigment absorbs the rest of the colors of light.
Chlorophyll is a green pigment found in the chloroplasts of plants, and it is an essential component of photosynthesis. Leaves often show a vivid green color when they are close to other leaves. This happens because the light people see bounces off the green leaves before it reaches the eyes. Chlorophyll utilizes mostly red and blue light energy, while the green energy passes through or bounces off the leaves and reaches a person’s eyes. Leaves then appear green. As autumn comes to an end, plants and trees produce less chlorophyll because light regulates the production of chlorophyll. Chlorophyll has a constant decomposition rate, and the green hue begins to fade when chlorophyll starts to decompose. Other pigments that affect leaf color are anthocyanin pigments that cause leaves to look red and carotenoids that cause leaves to appear red, yellow or orange.