It would seem that I'm very bad at explaining myself. This is not unusual, thus this clarification.
Imagine a flip dot display. 2 colors, one or the other, per flip dot or pixel, no substrate, no ability to adjust the intensity. The imagine that these flip dots are infinitely small, or perceivable, individually, and that instead of just 2, you can have n colors, of your choosing. You can even play with he idea that every other flip dot or pixel, has a different set of colors, but that one I think I can figure out for my own.
And then the actual question. What is the most versatile set of colors, for at set of a given size, and how do you figure it out?
--- original question ---
If I am not much mistaken, given enough resolution, with just 4 colors, perhaps even less, though I don't really think so, you can simulate the appearance of any color the eye can perceive, involving the concept of dithering, to mix the colors, without actually doing so, exploiting the limitations of human vision.
I have tried various approaches, the last couple of weeks, to figure out what those color might be, from studying data on the sensitivity of the L M S cones, in the human eye, to brute force manual and automated testing.
The results vary a bit, but generally the best results seem to involve yellow, red, a very light cyan, and of course black. There is no paper or background to provide a 5th or no color, so that is rather important.
However, I have also found other option, for example involving some variant of orange and/or purple and I have so far, completely failed to draw any particularly useful conclusions. Of course, my testing has been on the computer, in the emissive space, if you can put is like that, but I do actually plan to use this knowledge, in the reflective space, for a project I'd like to work on, in the future, which further complicates matters, as I have no idea how that conversion works, even after spending days on end, reading about, among other things, that particular subject.
In short, I may well have what I need, for practical applications, but I wouldn't know, and I'd very much like to understand it too.