Above is an image of Goethe's color wheel c.1810. I know..... Goethe was a poet, writer, philosopher kind of guy not a famous artist, but modern artists use color in profound thanks to great theorists and scientists throughout history. Newton, Goethe, Chevreuil, Itten, Albers, and Munsell are the names that come up most often when talking about color theory.
Goethe's wheel shows 6 hues, namely the three primaries (red, blue, and yellow), and the three secondaries (orange, green, and purple). Our artist's Color wheel shows 6 tertiaries as well (red-orange, yellow-orange, yellow-green, blue-green, blue-violet, and red violet) for a total of 12 Hues around the color wheel. Color Wheels show each Hue at its purest, and only show one dimension of color.
Itten's Color Star takes it up a dimension, by not only showing the 12 hues but also showing Value gradations for each hue from light to dark. The color wheels I had students do in class were more like Itten's star. However we just took each hue up and down one step by mixing in white and black. In class we sorted color chips on a table and found it difficult to place neutral tones. The difficulty was due to working on a flat surface- color is 3-DIMENSIONAL
Here is an image of Philipp Runge's Color Spheres also c.1810. You have to imagine color as a globe. Each longitudinal section represents a hue or color family with all of the purest colors on the crust. Each latitudinal cross-section represents a step on a value scale, with white at the North Pole (think polar bears) and black at the South Pole (think penguins). A Slice across the equator would show the color wheel around the outer edge with colors becoming duller at the core. This is the view that illustrates Chroma! Any slice across a hemisphere will show how opposite colors mix together and become grey. They cancel each other out and lose chroma.
So, Hue, Value, and Chroma are the 3 dimensions, the 3 characteristics of color. If you have any collections at home, try organizing them by H,V,C. Perhaps its a stash of beads or fabrics. Maybe it's your sock drawer. Whatever it is, see if you can make smooth gradations of color, and you may find it easier to find things! Check out this link to see some bookshelves arranged chromatically: http://www.flickr.com/photos/santos/27538777/