In addition to chlorophyll, lutein, carrots and other pigments, plant leaves also contain a special pigment called anthocyanin, which is a "chameleon" and is red in acidic solution. With the change of seasons, the temperature and sunshine increase or decrease correspondingly, and the main pigment components in leaves also change.

In autumn, the temperature decreases and the light decreases, which is beneficial to the formation of anthocyanins. At this time, the leaf cell sap of maple and other red-leaf trees is acidic, and the whole leaf is red. Therefore, it was the weather conditions in autumn that dyed it red.