text: why is the sky blue and the grass green? i accually know whay the grass is green because of the clorifil it just sounded cool grass is green because they contain a pigment known as chlorophyll. the chlorophyll is used in the process of photosynthesis where a plant produces sugar in the presence of sunlight.  blue sky:  a clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light.