Most leaves appear green because they contain chlorophyll, a pigment that absorbs red and blue light from the sun and reflects mainly green wavelengths back to our eyes. This reflected green light is what makes foliage look characteristically green in most plants.

The core science

  • Leaves are packed with chloroplasts, tiny structures in plant cells that hold chlorophyll pigments.
  • Chlorophyll absorbs light most efficiently in the red and blue parts of the visible spectrum, using that energy to power photosynthesis.
  • Green light is not absorbed as effectively, so it is mostly reflected and transmitted, which makes leaves appear green to human eyes.

Why chlorophyll is green, not black

  • Sunlight contains many wavelengths (colors), and chlorophyll’s molecular structure makes it especially good at absorbing red and blue, not green.
  • Because green wavelengths carry energy that chlorophyll does not use efficiently, they are left over and reflected, giving leaves their green appearance.

Not all leaves are equally green

  • The exact shade of green depends on the types and amounts of chlorophyll pigments, mainly chlorophyll‑a (bluish‑green) and chlorophyll‑b (yellowish‑green).
  • Other pigments (carotenoids, anthocyanins) are present too, but chlorophyll usually dominates in spring and summer, so green is what we mostly see.

Seasonal color changes

  • In autumn, many plants break down chlorophyll as they prepare for dormancy, so its green color fades away.
  • As chlorophyll disappears, yellow, orange, or red pigments that were hidden become visible, which is why leaves can turn bright colors before falling.

TL;DR: Leaves look green because chlorophyll absorbs red and blue light for photosynthesis and mostly reflects green light, so that is the color our eyes detect.

Information gathered from public forums or data available on the internet and portrayed here.