A triadic color scheme consists of three colors having a triangular relationship on the color wheel.
The basic triads are the primary, secondary and tertiary triads. They are evenly spaced around the wheel 3 colors apart from each other. The primary triad (violet triangle in the above photo) consists of red, yellow and blue; this along with the secondary triad (in their high chromas) is a favourite for children`s books, toys and rooms. It is a happy and colorful theme. A white background or white walls help bring these various, saturated colors together so that they donot clash.
A white background always gives a fresh (sometimes crisp) look to a painting. In the botanical paintings of Redoute` `s old world roses (Leafy white rose of Fleury, Unique Blanche rose for e.g) the white background really helps to bring out the delicate, fragile beauty of the petals. A black or dark background, on the other hand can be made dramatic or sombre and pensive.
I`ve done these from a chinese painting book a very long time back. It is an art form in itself but also is a fun way for practicing your brushstrokes.
The yellow triangle on the color wheel is an example of what is called the modified triad. They are spaced one color apart. It gives a little more contrast than the anaologous color scheme. Here is another example in which the blue-green-violet make a lovely combination:
A complementary triad consists of a complementary pair and the color halway in between them. The white triangle is an example. Another is yellow, violet and red-orange.
The split complimentary triad consists of a color and the two colors adjacent to its complementary. The red triangle in the wheel forms an example.