Black and white. As in, the "video" element of the games used a black and white monitor (tv) to display the graphics.
Personally, I think they are pretty cool. Since the game hardware at the time couldn't display much for graphics, they could rely on some of the tricks used in electromechanical games to create atmosphere. Overlays, reflection of the monitor image (think Asteroids Deluxe), innovative controls, and other things were used to make the game experience great.