Article: The Order of Attraction
A successful painting is not simply a well designed depiction of a pleasant subject any more than a successful novel is a grammatically correct description of an interesting event. Good art requires more than that. The artist must convey his personal response to the subject and direct attention to the important elements.
One way to do this in painting is by planning the placement and degree of contrast. This would be much easier if the three kinds of color contrast—value, intensity, and hue—were equally attractive to the eye. But they’re not. Read more about value, intensity and hue in this PDF.