Although Kline was known primarily for his large canvases featuring bold strokes in black on white, he also executed many works in color. While his color paintings were often small, they assert a capacity for expansion and imply a greater physical size that is comparable to Kline's large-scale works in black and white. Kline as a colorist has been seriously overlooked, and refutes his classification as strictly a black and white painter. Similar to the thrusting strokes found in his black and white paintings, Kline's use of color is expansive, bold, and exuberant. In his development as an abstract artist, Kline relied on color between 1946 and 1950 as he transitioned out of his figurative style. However, it was not until the mid-1950s that Kline fully developed his color filled abstractions, and the color works from 1956–1961, such as Untitled (1957), are outstanding examples of this genre. Kline's images are inspired by both urban and rural landscapes—the energy of New York as an ever-changing city or the tempo of Provincetown, where, from 1956 on, Kline spent part of his summers. His works allude to the city's partially demolished or constructed skyscrapers or evoke aspects of the sunlight, water, and air of the New England coast.
Untitled (1957) combines broad strokes of color, of black, and areas of unpainted ground. Saturated hues of green and yellow emerge from the composition, for example, acid yellow grounds in the bottom section of the work and a scattering of that color throughout the top section. Vibrant red orange dominates the upper right portion of the composition and contrasts with bold areas of green, heightening the sense of intense activity. Broad diagonal gestures—black strokes—bridge the upper and lower sections of the work, bringing the composition into equipoise. Here Kline gives equal weight to both black and color as they contend with each other for dominance. The rich colors—bright red orange, green and yellow—are as strong in their interface with the black calligraphy as the whites in Kline's black and white compositions. In juxtaposing black to color, color becomes a participant rather than an adjunct to abstraction.