George was also struck by Triumph of the Will. The Empire very much has strong Nazism influence but a little known fact is the ending of A New Hope borrows strongly from the propaganda piece for the Rebel Alliance medal ceremony. You see this repeated in Attack of the Clones to a degree with the Clones.
Here’s an article that cites it:
https://www.newyorker.com/magazine/2007/03/19/where-theres-a-will
Needless to say I think colours from the onset were inspired just as much by Western culture as a whole and not just one source. There’s also of course the strong Eastern influence. The films cited many reference points and cultures in designs as well.
Here’s also a great video of Camille Paglia discussing the ending of Revenge of the Sith: