Carotenoid pigments, responsible for the yellow and orange colors, also are located in the chloroplasts and assist chlorophyll in the capture of sunlight for photosynthesis. These yellowish pigments are always present in leaves, but are not visible for most of the year because there are larger amounts of green chlorophyll. As chlorophyll degrades, the yellowish colors become apparent and give leaves part of their autumn splendor. It is the unmasking of the carotenoids that account for the yellow color of Norway maple, Ohio buckeye, yellow poplar, sycamore, birches, hickories, ashes, and many other trees. The same process also accounts for the yellowing of leaves at any time during the year due to nutrient deficiency or disease that reduces the normal production of chlorophyll.
Tannins cause the brown hues in leaves of some oaks and other trees in the autumn.
Like the carotenoids, these compounds are always present, but only become visible as chlorophyll and carotenoids disappear from leaves. Tannins are bitter substances that color and flavor tea and cause unripe persimmons to pucker your mouth. They are common waste products of metabolism in trees, deposited in the cell sap inside the vacuole as well as in cell walls, and often accumulating to considerable amounts in dead tissue. The golden yellow produced in some leaves such as those of beech, result from the presence of tannins along with the yellow carotenoid pigments. Anthocyanin pigments are responsible for the pink, red, and purple leaves of sugar and red maple, sassafras, sumac, white and scarlet oak, winged euonymus, and many other woody plants.