As summer fades into fall, the days start getting shorter and there is less sunlight. This is a signal for the leaf to prepare for winter and to stop making chlorophyll. Once this happens, the green color starts to fade and the reds, oranges, and yellows become visible.

Why do leaves change colors?

Chlorophyll Breaks Down But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process. The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible and give the leaves part of their fall splendor.

Why do trees change Colour?

As the tree becomes dormant, a compound called abscisic acid triggers a seal to develop at the base of the leaves, before they fall off. This reduces water reaching the leaf and traps the chemicals remaining in the leaves. They gradually break down, changing the colour of each leaf before it drops to the ground.