I just finished taking a watercolor workshop with Gerald Brommer on content and emotion. The first day of the class he had us do 5 minute sketches of 12 landscape slides. We picked on of our sketches and did 2 paintings of the exact same scene. One painting was done as a high key (light valued) painting and one was done as a low key (dark valued painting). I definitely showed how the values change the emotion of a painting.