Many leaves change color in autumn as green chlorophyll breaks down. Yellow and orange pigments become easier to see, while some leaves also develop red pigments. The result varies with the tree and its growing conditions.
The green was hiding other colors
The National Park Service explains that chlorophyll helps leaves use sunlight and gives them their green appearance. As the season shifts and chlorophyll is dismantled, pigments previously hidden by that green become visible.
This is why “the leaves were painted yellow overnight” is a charming description but an incomplete explanation. Some of the color was already part of the leaf’s chemistry.
Red adds another part of the story
SUNY’s College of Environmental Science and Forestry describes yellow and orange pigments alongside green chlorophyll, as well as the development of red anthocyanin pigments during autumn changes. Different mixtures help explain why trees do not all finish in the same shade.
Daylight, temperature and water conditions affect the process. The sources support that general relationship, not a promise that one cold night will make every tree outside your window turn scarlet.
Watch one tree rather than a whole season
Try choosing one tree you pass regularly. Take a photograph from the same public viewpoint every few days and record the date. Describe whether you see mostly green, mixed colors or mostly bare branches.
If you compare photographs, keep lighting in mind: the warm light of late afternoon can make a scene look different from the same view under cloud. Record that difference instead of attributing every color change to the leaves themselves.
For an extra question, compare two nearby trees without assuming they are the same species. Your observations can show a contrast; identifying the biological reason requires more information. That is a useful boundary between noticing a pattern and explaining it.
The point of the exercise is to see a familiar place change, not to produce a regional foliage forecast. A single tree is already a good subject.
Read next: what causes the seasons, or another everyday color puzzle: why sunsets turn red and orange.
