Payne doesn't go into detail, but suggests that we read a variety of books on Color Theory. Mixing grays can be achieved by a mixture of three primary colors with either a dark or light. Payne prefers the use of a mixed neutral shade (warm gray) instead of black pigment, since black doesn't do well with color to mix this he suggests equal proportions of Indian Red, Ultramarine Blue, and Yellow. The 'soup' method of unity is mixing a dominant shade and injecting it in every color used. Payne suggests the best way to create harmony of color is to use a saturated color with a modified color (a tint or shade). Creating a color mixed chart is useful the artist can learn about the mixing and balancing of analogous and complementary colors. Mixing compliments on the color wheel result in muted neutral grays. Payne discusses primaries and the mixing of secondary and tertiary colors.
The challenge of using a Color Spectrum Theory for painting is that they are based on light rays, while pigment is an opaque material.
While not necessary for unity or composition, color is necessary to complete the unification of a painting.
