Why is the grass green?

Sunlight gives off UV rays, which plants absorb to turn into energy. This energy is called ATP. In order for photosynthesis to occur, ATP must be present. Because light comprises of all the colors of the Visible Light Spectrum, or Rainbow, all colors EXCEPT green are absorbed into the chlorophyll. Green is the color reflected and transmitted back, and that is why we see green in plants. (There's a whole lot more, but that's the basics).