False Color Games

[Manic49er]

Does anyone remember a category of games that displayed color on a b&w tv??
Of course it was a false color method. I remember you had to put a colred (yellow or orangey??) on b&w tv screen and I think the false colors were generated by flashing characters/backgrounds on/off screen at different rates, different frequencies gave diff colors.
Anyone know what the names of such games were and if any of them are saved in some type of archival format (p, p81, etc) and where?

Hopefuly thanx,
Manic49er