By the time Dorothy opened a door onto Oz in 1939, Technicolor — the company that let viewers see the yellow in the yellow-brick road — was already almost a quarter-century old.

This year, it turns 100. The breadth and variety of American films that used Technicolor processes between 1922 and 1955 are apparent in a recent book, “The Dawn of Technicolor, 1915-1935” by James Layton and David Pierce, and a continuing series at the Museum of Modern Art running through Aug. 5.

Technicolor can’t take credit for inventing color; that impulse existed from the dawn of movies. Early silents were commonly shown with hand coloring and tinting. Still, a workable approach to full color long eluded engineers, who had to overcome problems with speed, film stock, illumination, misaligned color components and eye strain.

In some early processes, black-and-white film prints were projected through color filters. Once it became possible to store color on the film print itself, Technicolor set itself apart from its competitors by developing a process that could work for studio filmmakers. Initially, Technicolor’s system recorded only combinations of red and green. Orange photographed well enough, but purple became a muddy brown.