All official Famicoms and NESs use the NTSC variation of the PPU. This generates its color signals along the I and Q axes. The Playchoice 10s, (but not the VS System), use the RGB variation of the PPU. This generates color through discrete values of the three primary color elements. But how close are the colors produced by the two PPUs? They are supposed to be 100% compatible, and modders have taken Playchoice PPU and put it into their NESs for RGB output. This does not mean they will experience the same colors as the NTSC chip would produce. It is difficult enough to get the same colors from one NTSC monitor to another, since they have contrast, brightness, tint, and color controls. Then again, Nintendo had the equipment to approximate the color wavelengths as closely as possible, while emulator authors do not.