For Richard Diebenkorn’s Girl on the Beach (1957), I am drawn to the painting’s gestures. I find my eyes following the impasto on the skirt to the expressive sand. The beach is a palimpsest of color. The unexpected hues remind me of the bright outlines in Wayne Thiebaud’s candy counters and frosted cakes. The painting is flat but with so much depth. The woman almost hollows out her spot in the center of the canvas. She sits with comfort and confidence, on the ground with her shoes kicked off,...