Why leaves change colour

Passage

In autumn, the leaves of many trees turn from green to brilliant shades of yellow, orange and red. The green comes from chlorophyll, the pigment that captures sunlight for photosynthesis. As days shorten and temperatures fall, trees stop producing chlorophyll, and it breaks down. This reveals other pigments that were present in the leaf all along but had been masked by the dominant green. The vivid reds, in particular, are often produced afresh as the tree withdraws nutrients before the leaf falls.