Contrary to the story that says some scenes of the film are in black-and-white instead of color because the production company was running short of money and saved money by having some scenes processed in monochrome, according to interviews with
Malcolm McDowell,
Lindsay Anderson and the cameraman, they first shot the scenes in the school chapel in monochrome because they had to use natural light that came in through the big stained-glass window, requiring high-speed film. The high-speed color stock they tested was very grainy and the constantly-shifting color values due to the angle of the light through the stained glass made it impossible to color-correct, as well. So they decided to shoot those scenes in monochrome, and, when he saw the dailies, Anderson liked the way that it "broke up the surface of the film", and decided to insert other monochrome scenes more or less at random, to help disorient the viewer as the film slipped from realism to fantasy.