"Yves le monochrome," as Klein called himself, saw the monochrome painting as an "open window to freedom, as the possibility of being immersed in the immeasurable existence of color." Although he used a range of colors before concentrating on three—blue, gold, and a red he called Monopink—he is most associated with a blue he named International Klein Blue, which he arrived at by working with a chemist to develop a binding medium that could absorb pure color pigment without dimming its brilliant intensity. A student of Rosicrucianism and of Eastern religions, Klein entertained esoteric and spiritual ideas in which blue played a vital role as the color of infinity. Keenly aware that pigment is a substance of the earth, Klein also devised methods to make paintings using the other three elements—air (in the form of wind), water (in the form of rain), and fire.
Kazimir Malevich's Suprematist Composition: White on White (1918) is the major historical precedent for recent monochrome, but Klein argued that the Russian artist's primary concern had been with form—the square—rather than with color. As a result, Klein felt that "Malevich was actually standing before the infinite—I am in it."
from The Museum of Modern Art, MoMA Highlights, New York: The Museum of Modern Art, revised 2004, originally published 1999, p. 242