Accessory pigments are
light-
absorbing
pigments such as
carotenoids and
phycobilins that serve as complements to
chlorophyll in
plants,
algae and
bacteria by trapping
light energy for
photosynthesis.
Some of these pigments in edible plants act as beneficial antioxidants when consumed by humans and other mammals. Thus, the more brightly-colored a fruit or vegetable is, the better it is likely to be for you.
Part of this writeup is based on work I did for the science dictionary at http://biotech.icmb.utexas.edu/