The purpose of color in illustration is to differentiate and connect, as well as to highlight and hide. The mixture of different hues and intensities bring modern media to life. We perceive colors in relation to one another, and therefore, it remains a shifting phenomenon.
In one of Bill Wattersons famous Calvin and Hobbes comic strips, Watterson sets a good example of how color can be used properly to highlight certain elements.
For example, the contrasting red against white, highlights Calvin in a way that he is able to stand out, since our eye is immediately drawn to him at the beginning of this comic. We then see the use of analogous colors in the box where the background appears a desaturated blue against the saturated blue of the balloon. These two colors has related color temperature, and are therefore able to soften and create a certain energy and mood (in this case, surprised).
The next box contains a fully saturated green background, and since green compliments red, this is typically the first thing you look at when you pick up this comic strip. The rest of the background is white, so this really stands out. Watterson chose to use mostly primary colors to fill in his illustration, but the slightly hued colors of pink/purple and blue bring the uniqueness and importance to this particular comic.