This is the third in a series of posts about color for painters. In the first, I established (to my satisfaction, anyway) that the usual advice on color that you see in most books on painting, based on a three primary color wheel, is not very useful. In the second, I described the Munsell color system, which provides a useful approach to describing color, although it doesn’t say a lot about how to mix pigments together.
That all being said, the Quiller wheel (or something like it) is a useful tool that can be helpful, especially for beginners, in figuring out the basics of color mixing. There are other mixing wheels out there, sometimes with fancy sliders that you can turn around a cardboard wheel. There is also color mixing software that attempts to do the same thing. They all have significant limitations when it comes to making subtle mixtures of actual paints.