What is a green colored substance that helps plants use sunlight for photosynthesis?

chlorophyll

The "green substance" is chlorophyll, a green pigment found in the chloroplasts in a leaf. Chlorophyll traps sunlight for photosynthesis- a plant's way of making food for itself using sunlight.

Photosynthesis equation:

sunlight

carbon dioxide + water -------------------> oxygen + glucose

chlorophyll

6CO2 + 6H2O ----------------> 6O2 + C6H12O6