I have green grass. Lots of it. Nothing added except lime (once), and some straight fertilizer every few years.
A picture is worth a thousand words. Would you like me to post a picture of my lawn? Only one section is lousy: Where the utility company dug it up to work on the pipes, and then planted with something which must've been 50% weed seeds. That'll be fixed easily this month, without herbicides.
If you actually need an explanation, that must mean you really don't understand the plant around which your career is centered. How can that be?