Okay, this isn't my planned third attempt, it's just something I had a play with. I can't put a scrolltext in it or anything that would stop you from following objects up the screen as it would destroy the effect. As a result, I'm not sure it would benefit from music either.
Anyway, the screenshot gives the game away as to how it works. There is no palette switching, no flashing colours, just four colours, black, red, green, and blue.
It doesn't need a seizure warning but if you watch it for long enough, I wouldn't advise walking or trying to do any fine motor control for a few minutes as your eyes will still be trying to look up.
[EDIT] I forgot the darker shades of red, green, and blue. I've modified the exe and screenshot to reflect the change. I don't think it can count as 10 actual colours though.