Chlorophyll is a molecule that has special properties suitable for absorbing light and harnessing its energy for use in the cell. Unfortunately for plants, it happens to absorb light best at red and blue wavelength, even though sunlight is more intense at green wavelengths. Since chlorphyll reflects green wavelengths, it makes plants appear green.
Plants use supplemental red pigments called carotenoids to collect the green wavelengths that chlorophyll can’t absorb, and pass the energy on to chlorophyll.
Even so, because they have so much chlorophyll, plants reflect more green than any other wavelength, which is why they appear green.
In the fall, when chlorophyll breaks down, the carotenoids are revealed.