Autumn bike

The spectacle of green leaves turning rich reds and yellows in autumn happens when trees have taken all the food they can from the leaves that are filled with chlorophyll – the biomolecule that absorbs energy from sunlight and gives leaves their green colour. When sunlight wanes and leaves stop making food, this green pigment is broken down into colourless compounds. Yellow pigments are then revealed and other chemical changes cause red colouration. (source)