I thought to try the other combination. If not both of the restrictions are necessary then I think the other half remaining would be a high res thing with just 4 colors. Maybe not so oldschool as the lowres thing but I decided to try something I had in mind.
It's just an effect with shifting chess arranged colors, where the high res of the think hide the fact that it's just 4 colors and not 7 (well the most possible combination is 9 or 10 I think but no time). Just press screen to check a screenshot. Well, it would be even greater if I had time to make some more colors and interpolate between them at each frame (4 colors at once but I could circle the pallete). Pitty I don't have time because it would look greater. And maybe I could fix the bad edges there. At least I am happy about the colors

That's it. I have to go out now, no more time to improve this..