Why are plants green?

Green coloration comes from the reflection of light off of a plant's cells. The plants cells are full of photosynthesizing chemicals called chlorophyll which reflect a green color. Not all plants look green though, due to the ability to reflect other wavelengths of light. When plants lose chlorophyll they will tend to lose the green color. This is why plants lose their green color in the fall and turn into red, orange, and yellow.