Only for the NES2:
http://www.gamesx.com/rgbadd/nes2avmod.htm
If you are trying to mod a NES1 you need to change out the PPU so it generates RGB.
Use this one for the nes2 instead. It's loads better. You'll have to cut pin 21 and lift it up but it removes the lines that make the nes2 infamous.
http://darthcloud.da.funpic.org/img/bypass.html