Why are most plants green?

Chlorophyll is the pigment that captures light energy to power photosynthesis inside chloroplasts. Its two main forms, chlorophyll a and b, absorb strongly in the blue and red parts of the spectrum. Green light in the middle of the spectrum is absorbed less efficiently, so much of it is reflected or transmitted, making leaves appear green. Scientists have proposed that this may help protect plants, since absorbing too much energy at the peak of sunlight can damage their machinery. Plants also contain other pigments such as carotenoids, which become visible as yellows and oranges when chlorophyll breaks down in autumn.