Here is a demo that uses "interlaced" flickering to get a four-color screen using just the background and playfield colors. The screen isn't interlaced in the normal TV sense of the word, because there are only 262 (not 262.5) scan lines per field/frame. However, the colors and data bits (pixels) of the two frames are alternated, so each frame essentially contains lines from two different fields which are interlaced together, thus making the flickering undetectable (at least on my TV, to my eyes