The professionals (like in this really good book I got from the library) suggest that doing some work seeing how your colors blend together is worth the time and effort. I like to use Premo. It has a couple of kinds of red, yellow and blue, so I wanted to see how they blended together at known ratios. I worked more or less in fourths. I sheeted some of each of the three primaries, plus a second shade of blue, and cut them into 1/2" squares. Then I blended ratios starting with one square to three squares, two to two, and so on.
The results were interesting! With the orange at the bottom, I was surprised at how little red it takes to make orange. The blend on the right in the last row is something like 5/4 yellow and 1/16 red.
It's hard to follow on the picture (I have notes, though, honest!) but the blue-green and blue-purples are using two different blues, and they gave different results. The end of the second row are the cobalt-yellow samples, and the third row is ultramarine blue-yellow. The cobalt made much more pleasing greens, I thought. Same kind of thing for the purples. The top row and the first five of the second row are similar ratios using the two different blues.
You can see how the possibilities, while not endless, are many and I just scratched the surface of making a record of color combinations. I could also tint them with white and/or black. I use metallic accent clay, too, which changes the color, so that's another set of possibilities.
Now if I can get my act together, and I really should because this can serve as a reference kit, I'll sheet each of these, cut out a circle , etch a number on it that corresponds to my notes, and poke a hole so I can string them on a piece of yarn and keep them nice.
I mixed colors later to make more small clay tiles and used what I had learned to make a serviceable copper color. Time well spent.