Simply Science 04
Grass appears green due to a pigment called chlorophyll, which is important for photosynthesis in plants.
Photosynthesis is the process where plants, including grass, convert light energy from the Sun into energy to fuel their growth and produce their own food. Chlorophyll is the pigment responsible for capturing light energy from the sun and using it to convert carbon dioxide and water into sugars and oxygen. This process occurs in the chloroplasts which are specialised structures within plant cells.
Chlorophyll molecules strongly absorb light in the blue and red parts of the visible light spectrum but reflect and transmit light in the green part of the spectrum. This means that when sunlight, with a range of colours, shines on grass, the chlorophyll in the grass absorbs most of the light except for the green wavelengths which it reflects. Our eyes perceive the reflected green light, giving the grass its characteristic green colour.