To use the sunlight, the plant must have a mechanism for absorbing the light.
Plants use chlorophyll and carotenoids, both chemical pigments, to absorb light.
Light has color components collectively known as the spectrum. The spectrum consists of red, orange, yellow, green, blue, indigo, and violet. The green light portion of the spectrum is not effectively absorbed by chlorophyll in plants. The green light is either reflected by or passed through the leaf. This is why leaves generally appear green.