I've been asked to explain my love of color charts, and a simple how and why to do them. Made famous by Richard Schmid in "Alla Prima–Everything I Know about Painting", now in its revised publication. He credits HIS tutor, Bill Mosby, with the idea of charts. Who knows where Mosby came up with it...the why artists pass along information, so it will never die.
In a nutshell, you are exploring your set palette (the colors you squeeze out every time you paint, hopefully in the same order) and how any two pigments plus white make new mixtures. Yes, you can purchase these in tubes, but I can mix mine in the time it takes you to find the right tube! With only two colors, you minimize your chances of mixing mud, eliminating the guesswork and wasted pigment (and time).
The entire article is available as a free pdf here: http://axully.com/art-workshops/
A companion article explores how color swatches on your computer can be put to use with the color charts. Enjoy!