Dufaycolor, only one feature film used this process.
I was watching an old colour movie today and noticed it used a colour process called Dufaycolor, it was called Sons of the Sea and was made in 1939 just months before the start of WW2. Unfortunately this version was digitally remastered so I wasn't able to see how the colours originally looked. A comment on IMDB by someone who saw it in 1940 said that the colours were vibrant. This movie was the only feature film to be made in Dufaycolor, WW2 put a stop to future use.
If anyone is interested there is more information on this process on Wikipedia and on IMDB