We stare and stare at color wheels, and most people don't use them at all, except maybe for figuring out a color's complement. But mixing with split-primary colors make beautiful hues. 80% of my painting is done with six primary colors and four convenience colors. I use a warm and cool of each red, blue, and yellow for my primary colors and create a split-primary color wheel with them.
To create your own, first draw a large circle on a 1/4 watercolor sheet, and place 12 circles (about 2" diameter) around the wheel, with the large circle dissecting each smaller one... like a clock. Divide it in thirds... noon, 4:00, and 8:00. You will place your warm and cool primary colors top and bottom in these circles (inside and outside rings). Starting at noon, place a cool yellow (I use Hansa Yellow) on the outside of the ring and a warm yellow (New Gamboge) on inside of the ring. Label them so you know the pigment you used.
Next, move to the 4:00 space and place your cool blue (Phthalo or Winsor Blue) on the outside and a warm blue (French Ultramarine) for the inside ring. Rotate your paper to 8:00 and place a cool red (Permanent Alizarin or Permanent Rose) on the outside ring and a warm red (Napthol, Winsor Red or Scarlet Lake) on the inside.
What do you do with it now? Well, the rule is, that when you mix two colors on the wheel, don't cross the center line! In other words, mix a warm with a warm, or a cool with a cool... in order to get a high intensity of color. When looking for a slightly grayed down version, like an olive-green, mix a warm with a cool - New Gamboge (W) with Phthalo Blue (C). Using these rules, you will never wonder why your color mixing is muddy again! I also have four convenience colors… quinacridone coral, burnt sienna, phthalo green, and permanent alizarin crimson. With these additions, I can make electric oranges, rich blacks, and luminescent grays.
Why does this work? Mixing complements together will neutralize your color mixture. In our olive-green example, you are making green with New Gamboge,which has red in it. The red neutralizes the green and dulls it down. One thing that I did notice in my own palette, is that even though Napthol Red and Permanent Rose are distinctly different reds, the secondary and tertiary colors were very similar. This is one reason why I have coral in my palette, for those times when I need a brighter secondary color.
With all those "rules", the last rule is - break them! Experiement and notice the results. Sometimes an artist can find a color mixture in different brands that produce lovely results when you don't expect it. Now, go forth and make a mixing color wheel... and try it out! See what results you get when mixing both high intensity mixtures and low intensity mixtures.