Vincent Van Gogh, Portrait of Joseph Roulin, 1889. Oil on canvas, 25" x 22."
Agony is generally upon as the animating factor in Van Gogh's paintings, but I tend to disagree. When he's really good, it's because of the color; he might be one of the best intuitive colorists in western painting. It even took him by surprise - in his letters to Theo, he describes in great detail his struggles with drawing, and expects to wrestle with oil paint as much as he did with charcoal and watercolor. But in a letter dated August 20, 1882, he states with wonder: "Painting comes easier to me than I imagined, and perhaps the right course would be to put all my effort into it, toiling away at the brush before anything else, but I must confess I'm not sure." His reservation was the cost of materials: "I don't want to push either of us into unnecessary expense, but it is plain that the painted things have a more pleasing aspect."
Van Gogh painted this portrait of his friend Joseph Roulin at Arles in 1889. The entire picture is essentially oppositions of blues and greens against reds and oranges. The effect is most striking in Roulin's green eyes, which are rimmed with strokes of red-orange. They strobe a little (as close-value, high saturation complements tend to do) and this same color treatment is applied to the postman's cheeks in a much more muted way. The face, portrayed in a calm expression but vibrating with energy because of the touches of color dissonance, is then framed with that swirling wallpaper and beard, again using controlled flashes of color opposites. The whole thing is anchored with the large areas of blue in the coat and hat, which keep the composition from just turning into a spinning blur.