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 mainly because, although French authorities allowed Nazi swastika flags to be displayed on public buildings for crucial shots, they refused to permit the flags to retain their original red color; consequently, green swastika flags were used, which photographed well in black and white.