The film was shot in black and white mainly because, although the French authorities would allow Nazi swastika flags to be displayed on public buildings for key shots, they would not permit the flags to bear in their original red color; as a result, green swastika flags were used, which photographed adequately in black and white.
The film was shot in black and white primarily because French authorities permitted Nazi swastika flags to be shown on public buildings for important scenes but did not allow them to keep their traditional red hue. As a result, green swastika flags were utilized, which captured well in black and white.