Autumn colour is all a result of our deciduous trees settling down into their winter routine and abandoning their leaves.
During spring and summer, the chloroplasts within the leaves combine sunlight, water and carbon dioxide to produce sugars to feed the plants and release oxygen. As temperatures fall and days shorten, the benefit from the leaves diminishes until it becomes a losing equation and the leaves are relinquished. Before this happens, the chlorophyll within the leaves, which has given them their green colour, is reabsorbed by the tree. The other colours within the leaves, which though present throughout the life of the leaf were disguised by the chlorophyll, can now be seen clearly.