The simplest color wheel consists of a circle divided into six equal wedges. You color the top wedge, say, in yellow (the first primary color). Then going clockwise, you skip a wedge and color the next one in, say, blue (the second primary color). Finally, you skip another wedge and color the next one in red (the third primary color). The respective uncolored wedges will be filled in with the secondary color produced by the mixture of the two neighboring primary colors.

None of the tube colors you can buy in the art stores are pure. For example, both Lemon Yellow and Cadmium Yellow obviously look yellow. However, if you mix these two yellows with another color, say, Cadmium Red you will get two different oranges.

In general, tube color mixtures will yield secondary colors that do not always answer your expectations. Sometimes they will be really off. You may, for example, expect green but get a dirty brown instead.

This reason for this is that tube colors invariably have one or more undertones, i.e., colors that are different from the dominant hue and are present in small amounts. It is these undertones that can change the expected character of a mixture in often drastic ways. So, it is true that red and yellow, for example, generally make an orange but certainly not always a clean orange and sometimes even a color that cannot be called orange.

However, the palette consisting of the following three tube colors will always give you very decent secondary colors:

1. Lemon Yellow
2. Permanent Rose
3. Phthalo Blue (Red Shade)

Here are the properties of these three tube colors:
Note that White and Black are generally not classified as colors.

* Lemon Yellow - Lemon Yellow is a cool, greenish leaning, and opaque yellow. This yellow is a medium-to-slow drier with medium to low tinting strength.

* Permanent Rose - Permanent Rose is a cool, violet leaning, and transparent red. This red is a medium-to-slow drier and has a medium tinting strength.

* Phthalo Blue (Red Shade) - Phthalo Blue is a cool, green leaning, and transparent blue. This blue is a medium-to-slow drier and has a very high tinting strength.

These three primary colors are made from synthetic organic pigments and produce very agreeable and clean secondary colors. Lemon Yellow and Permanent Rose despite their respective leanings still make a clean orange mixture. Phthalo Blue (Red Shade) and Lemon Yellow yield an excellent green. Finally, Phthalo Blue (Red Shade) and Permanent Rose result in a first rate violet.

It is possible to improve on this three-color palette if we use two versions of each primary color. We choose them in such a manner that, for example, one version of yellow has an orange bias (i.e., leans towards orange) and the other version of yellow has a green bias. Similarly, one blue will lean towards green and the other towards violet. Finally, one red will lean towards violet and the other towards orange.

Here then, is the ideal six-color palette:

1. Lemon Yellow (green bias)
2. Cadmium Yellow (orange bias)
3. Cadmium Red (orange bias)
4. Permanent Rose (violet bias)
5. French Ultramarine (violet bias)
6. Phthalo Blue (Red Shade) (green bias)

Now, Lemon Yellow and Phthalo Blue (Red Shade) will give a superb green because both colors have a green bias. Similarly, Cadmium Yellow and Cadmium Red will give a brilliant orange because both have an orange undertone. And Permanent Rose together with French Ultramarine will produce an outstanding violet because they both have a violet bias.

Together with Titanium White and Ivory Black the above six colors form an excellent beginning palette that can produce an amazing number of excellent secondary and tertiary (i.e., a mixture of three or more colors) colors.