Ellsworth Kelly explored the relationship of color and shape in celebrated paintings, prints, and sculpture starting in the1950s. Although he developed a distinctly abstract vocabulary, his monochromatic blocks and arcs of evenly applied color were informed by observations of the world, including its architectural details, play of light and shadow, and natural forms. Among the artist’s innovations was a consideration of the way the shape of a positive form activates the negative space around it. For example, "Green Red Yellow Blue" consists of four brightly-hued panels spaced apart to incorporate the white of the wall into the overall composition. Similarly, the individual bold shapes of Kelly’s prints cut dynamically into the white of the paper. The energetic black and white lines of "River II" demonstrate another of Kelly’s interests: the role that chance can play in arriving at compelling compositions. Intrigued by cut-down pieces of trial proofs that he had rejected for a print project, Kelly enlarged and repeated four of the fragments, each of which depicts the details of his own brushstrokes. From those he created an eight-section grid.