This is from one of the film's pilots.
"There were actually two Triplanes used during the filming, the one just shown with the three cooling holes is an ex-Blue Max machine, with a Seimens engine from a Jungmeister, which was only used briefly. It hadn't flown in years and had some maintenence issues. The other one has a 180 Lycoming and is owned by the Real Aeroplane Company in Breighton, Yorkshire. It did the bulk of the Triplane flying for them filming, and was painted in Jacobs' colors originally, changed for the villian in the movie, and repainted red when required. We practically begged them to change the crosses, but for some reason the owner didn't want to do it, I think they thought the movie paint might be harder to get off than advertised. I think it was originally intended to leave that one black and use the other one for the red ones, but when we had trouble with the 2nd triplane the black one ended up being painted red when required and they had to deal with the movie paint all over after all, and it was a lot harder to get off than was thought.
The roman numerals I believe are to represent victory totals, so "crossed swords" had more than "black falcon", but was a nicer bad guy....
We pilots were a little worried that they were going to get carried away with decorating the Nieuports, but they ended up being just right for the task at hand. It was realised that with so many similar aircraft it could be hard to recognize who was who during dogfights, and so the topic of wing decoration came up. I suggested the Nungesser red-white-blue wing stripes, which they put on the Rawlings plane, and you can see that they looked at some WW1 books to choose some of the other emblems, like the "W" on Cassidy's Nieuport, copied from Harold Willis' SPAD, and the red bar across the top wing of Skinner's plane, which I believe was also copied from a real Nieuport.
The personal emblems on the Nieuports were vinyl stick-ons, which they changed regularly, giving me the chance to collect some souvenirs from the filming, which will decorate my hangar wall some day. The props guys were really busy all the time, changing the markings on airplanes, weathering them, and etc.
One of the really neat things there was the old lorries from the action vehicles guys (who were always the first in line at lunch time...), they were made from 1950s truck chassis with WW1 looking bodies built on them (and changed as needed), and to simulate the wheels with solid rubber tires they used idler wheels from old (1950s also, I think) tanks! The same guys had supplied tanks and other vehicles for "Saving Private Ryan", "Band of Brothers", "Sahara", and others. Lots of ingenious stuff going on on the set and at the studio."