If this limitation were to be chosen it would limit the amount of Hue’s you would be able to use, not individual Hex or RBG values. You’d be able to use the entire Value range (black to white) and saturation. Only one hue would be allowed on screen per frame. If we look at a HSV(Hue, Saturation, Value) or HSB(Hue, Saturation, Brightness) color picker you’d get to use the S and V/B and one H value per frame.
Tl;dr: It’s monochromatic