This is a tricky question. I can see that the grass is green because I associate the colour of grass with the word “green”. But I won’t know for sure if the “green” that I see is the same “green” as what another person sees. You might be seeing “blue” for all I know.
White light is a mixture of red, orange, yellow, green, blue and indigo/violet light. Plants like grass have a molecule in them called chlorophyll and chlorophyll absorbs red and blue light. This means that green light is unwanted and is reflected by the blades of grass. It’s the reflected light that we see, because the other colours are missing. The plants use the energy they get from red and blue light to turn carbon dioxide and water into sugars through photosynthesis. The red and blue light has the right amount of energy to be used, green light doesn’t.