Color or Colour Theory!

You have to know your tools for any trade.  It is so important to understand your tubes of paint.  My palette usually consists of:

1. Cadmium Red Light
2. Permanent Alizarin Crimson
3. Cadmium Yellow Light
4. Phthalocyanine Green
5. Prussian Blue
6. Ultramarine Blue
7. Yellow Ochre
8. Burnt Sienna
9. Cadmium Yellow Deep
10. Dioxazine Purple

The color right out of the tube is on the far right and I added white to them for the gradient.

Below, top left I mixed Burnt Sienna with every other color on my palette, next Cad. Yellow Deep and so on till I had a chart of all the color mixtures on my palette, mixed with white.  I'm not saying this is the palette to use, it just works for me.  Being mostly a portrait artist I'm using a lot of flesh tones.  Brands of paint are also different, so make sure to use the brand you plan on painting with.  I use M. Graham Oil paints. 

Not only is this a good exercise to do but after hours of painting, just like any other activity your brain gets tired and it's a good reference for those times when you are trying to match a color.