Ask Dr. Universe

Why do leaves change color? –Lucy, 5, Seattle, WA.

Dear Lucy,

Ever since I was a kitten, I’ve loved picking up big maple leaves in the fall. I’d take them home, put them under a piece of paper, and rub the side of a crayon over the top. It makes a great print of the leaf.

Leaves actually get their color from things called pigments. While scientists can use chemicals to make different crayon colors, nature can use pigments to create its own colors.

When leaves are green, they have a pigment called chlorophyll. Chlorophyll is not just important for color, though. Plants also need chlorophyll to...