Why do leaves change color from green to red and yellow in the autumn?

During summer, leaves are packed with green chlorophyll, which masks all other pigments. As days shorten and cool, trees stop producing chlorophyll to prepare for winter dormancy. As the green fades, the underlying yellow (xanthophylls) and orange (carotenoids) pigments are finally revealed, while trapped sugars produce brilliant reds (anthocyanins).