So kind of the way ink on paper adds black to make CMYK, the screen would add black to make RGBK? That would be awesome! I wonder how hard it would be to line u

So kind of the way ink on paper adds black to make CMYK, the screen would add black to make RGBK? That would be awesome! I wonder how hard it would be to line up two independent displays? They'd need to be pixel perfect.