By the late mid-1950s, Kline had refined his black and white paintings and arrived at new innovations. In 1956, the artist introduced color to his black and white abstractions, selectively and with great bravado. The second innovation included two large mural-like paintings in 1959, one being Orange and Black Wall and the other, Washington Wall. The latter has been described in the literature as a cinemascope. There is an element of theatricality built into this work. The work can be seen in stages, which includes the introduction, crescendo and the denouement of the image. What is also notable about this painting is the combination of opposite directional pulls to the extreme left and right sides, which is the basis for its sheer vitality.
The addition of color, usually bright and unmodulated, to his abstractions occurred during a pivotal moment in Kline's career. He changed dealers and in 1956, began showing works at Sidney Janis Gallery, which brought him higher visibility and greater acclaim. His works were regularly included in the Americans exhibitions curated by Dorothy C. Miller at the Museum of Modern Art. While the critics at that time denounced it as a risky move to introduce color, Kline took on the challenge of painting with color to produce the same extraordinary combination of dynamism and gravitas, which previously only the black and white abstractions were thought to possess. He used color as the means to add visual complexity to the structure of the composition. Washington Wall consists of numerous vectors and strong diagonals, which give the picture the appearance of tautness and vitality. Aquamarine blue, green, brown and red work in concert with the black and white to carve out space within the picture. Every mark appears spontaneously rendered but the overall image is a very complex one, where brushstrokes are constructed in an architectural fashion.
In discussing the addition of color to Kline's painting in the 1950s, one must consider Kline's close friendship with de Kooning, who considered Kline to be his "best friend." Together they ruled the artistic intelligentsia on Tenth Street and captivated and influenced younger artists with their inimitable yet accessible styles. In 1955 de Kooning reverted to painting strictly abstract pictures after painting women, but this time, he used bright, undiluted colors. His paintings like Police Gazette and Gotham News, both from that year, include energetic slashes of red and blue paints and built-up layers of yellow paint. While de Kooning may have not been a direct influence, his new work was known to Kline. In Washington Wall, the colors meld to the planar surface of the image; additionally the colors for the most part do not act independently from the black and white brushstrokes. For Kline, the nature of his painting did not change with the addition of color. He had once stated, "an area if strong blue or the interrelationship of two different colors is not the same thing as black and white. In using color, I never feel I want to add to or decorate a black and white painting. I simply want to feel free to work both ways."
What is remarkable about this painting is the incorporation of the dimension of time. Usually his images are immediately apprehended. With Washington Wall, the viewer must "read" the painting almost sequentially in order to get the full effect of the image, given the unusual format of the painting. It has a sense of the narrative that is about to unfold. The two strong diagonal lines that jut out from the right side of the picture to the very end on the other side contain incredible velocity. Interspersed among the diagonals are triangular white areas that contribute to the feeling of acceleration. While the composition is asymmetrical, proportionally, it is a balanced picture because the white area of the left section has great tonal value and acts as the passive foil to the active brushwork. Kline often used an edge or the side of the canvas to lay down the groundwork for the image, rooting it and from there, bursts forth explosions of paint.