Contrast
Contrast in coloring-in can be incredibly effective. While its not exactly an aspect of color theory, we will look at contrast in terms of color use. Contrast is one of the principles of design. The principles of design are guidelines for creating an aesthetic composition.
Contrast is a difference in value, in color, in texture, in size, or in degree of detail. There can be areas of high contrast or low contrast, or any number of relative degrees of contrast.
Studies have shown that the human eye is attracted to areas of contrast. For this reason, areas of high contrast are sometimes called areas of emphasis. Designers can encourage their audience to look first at the main topic by making certain that this area exhibits more contrast than any other area of the composition.
A good way to achieve contrast (and one you have read about before in this series) is to use complementary colors.
Complementary colors draw your eye to the green set of ornaments. Contrast, creates focus.
Warm and cool colors when used in close association create contrast.
The warm and cool colors of this image, not only identify the characteristics of the two elements, they also help to single out what aspects of the image belong to each.
To draw the viewers eye to a specific, highlighted, object focus the contrasting color on that place of the design you are coloring. This works well with light and dark, or bright and subdued colors.
Light and dark contrast is why coloring pages with printed black backgrounds really make the colors you add it pop out.
Coloring techniques can also create contrast. Smooth areas of color from your application process will appear visually different from areas filled in with a choppy application process.
 The different application techniques in this image create a textural contrast. Smooth sky and clouds vary from the mottled pointillism dots of the octopus’s body and the more wispy feathery strokes for the wings.
Coloring page examples from When Octopods Dream, Celestial Love Song, and Ornaments as published in Color On! Magazine.