Why do leaves change color in autumn?

As autumn approaches, the amount of daylight decreases, which signals trees to prepare for winter. This causes the breakdown of the connection between the leaves and the tree, reducing the production of chlorophyll, the green pigment in leaves. Without chlorophyll, other pigments such as carotenoids (which produce yellow and orange hues) and anthocyanins (responsible for red and purple tones) become visible. These colours were always present but were masked by the dominant green of chlorophyll during the growing season.