Rouxcolor is a color film process created by Lucien Roux and his brother Armand in 1947 in France. It was presented at the time as revolutionary compared to other processes such as Technicolor. Using black and white film, the color effect is obtained by a special lens that, during the projection, broadcasts four simultaneous images rendering the color. Marcel Pagnol used it on 1948 for "La Belle Meuniere". Filmed as a promotion for Rouxcolor, the result turned out disappointing. If the outdoors shooting were conclusive, the colors of the interior scenes were too loud, not to mention some technical constraints. The screening of this great film Rouxcolor did not meet the expected success and the project will finally be abandoned, despite a laudatory article in the New York Times during his presentation to the United States.
The process was used for the first two color egyptian films Father wants a Wife (1950) and The Lady of the Castle (1950) produced by Nahas Films and shot in the Studios Nahas in Cairo Egypt.
More technical details of that process can be found here as well as the Time Magazine press review dated 1948