Lots of people prefer their grass unpainted, apparently it tastes better that way. Also beware of paints with flammable solvents - when you light up some of your grass for a relaxing smoke you could get a nasty surprise.
Just wallpaper it instead - and you could finish off the edges with some coving. But be careful when you mow the sky, the birds don't like that.
Use an artificial grass. It might cost more in the beginning but think of the time you will save on mowing. If you have allergies to grass you won't have to worry either. Peace