Well, currently ArtRage doesn't have a special panel for mixing colors. I've read a few other posts from people interested in a mixing panel, but I'm not sure what plans they have for future releases of the program. I don't believe you would always get the results you were looking for, in the traditional sense anyhow. The color blending tends to work more towards a computer style of thinking, where if one were to take yellow and start pushing it into blue, one would end up with more of a gray color rather then the expected green. Again, this is something that has been posted by others in the past, but whether future versions of ArtRage will adopt it is unknown at this time.
As for color wheels, you could load a picture of the color wheel of your choice as a reference image and grab the colors directly from it (just hold "alt" and left click over the color you want to use). You can also create your own "color sample panel", which you can bring up by hitting the "s" key on your keyboard. Also, you could add an actual image into the color picker area (the color fan at the bottom right). Please view the attached image for an example.
Nothing is easy to the unwilling.