“The Rotocolor process was an additive system for color cinematography. The process was announced in 1931 by H. Muller. According to an article in Film Daily, April 12, 1931, and The Motion Picture Herald, April 11, 1931, the process consisted of a shutter device attachable to a standard projector. The device was easily removable permitting switching between black and white and color. Apparently the system was not commercially successful since no further mention appears in either the trade or technical literature. Examination of the patent literature 1927 to 1940 failed to uncover any patents for colour motion pictures granted to Mr. Muller.”
(Ryan, Roderick T. (1977): A History of Motion Picture Color Technology. London: Focal Press, p. 37.)
Anonymous (1931): Committee Activities. Report of the Color Committee. In: Journal of the Society of Motion Picture Engineers, vol. 17, July 1931, pp. 116-134, on p. 117.
Ryan, Roderick T. (1977): A History of Motion Picture Color Technology. London: Focal Press, pp. 37.