Learning to mix your own paint colors can save you a lot of money. Instead of buying every individual color you need, you can buy just the three primary colors--red, yellow and blue--and mix them as needed.
Basic Color Theory
There are three primary colors: red, yellow and blue. Mixing any two of these colors results in the secondary colors. (Yellow and blue create green, for example.) Violet and orange are the other two secondary colors. A color wheel is a device that features all of the colors created when these six secondary colors are mixed again to create tertiary colors. A color wheel is a great tool for understanding color relationships.
Browns contain all three of the primary colors, so different shades of brown are created by mixing red, yellow and blue. Another way to create a brown hue is by mixing a color with its complementary color--for example, red with green. Since green is a secondary color containing blue and yellow, all three primary colors are present. The other two complementary color combinations that will create brown are blue mixed with orange and yellow mixed with purple.
Color theory is based on light, not on the pigments ordinarily found in paints. So making brown paint by mixing the vibrant colors described above will probably not be aesthetically pleasing. The results tend to be dull and muddy. More likely to be acceptable are browns created with paints that have ochre, sienna or umber in their names. According to Kevin McCloud in his book "Complete Book of Paint and Decorative Techniques," these paints contain earth pigments like iron oxide.
A Starting Point
To experiment with brown hues, start with white paint using either artist's acrylics or oils. For a shade resembling pine, about half of the total amount being mixed will be white paint. Add another third raw sienna, then much smaller amounts of raw umber and yellow ochre. Burnt sienna can also be added. For oak, the white paint will be about a sixth of the mix. Add one-third yellow ochre, one-third burnt umber and about as much raw umber as the white paint. Mahogany is redder, so add small amounts of red ochre and alizarin crimson while decreasing yellow ochre. Burnt sienna and raw umber can also be added. Mix as you go when adding the colors to avoid adding too much. Experimenting while keeping a log of the mixes you try will lead to a personal library of brown hues that you like.
There is no need to limit experiments with brown colors to just the ochres, umbers and siennas. Blues and other colors will all lend their own character to the finished result. If too much of another color is added and your paint becomes too green, for example, add a little bit of red, its complement, to counteract this. Adding black to paint mixes does darken the color, but it also dulls the vibrancy of the paint, so do this with caution.