In autumn, chlorophyll is degraded in the leaves of deciduous trees. why do the leaves change color to shades of yellow, orange, or red?

Chlorophyll normally masks the yellow pigments known as xanthophylls and the orange pigments called carotenoids - both then become visible when the green chlorophyll is gone. These colors are present in the leaf throughout the growing season ... The only pigments that remain are tannins, which are brown.