I think that happened with "The Patriot" as well, despite The Smithsonian having put together a book of uniform patterns for them - apparently, someone decided that US audiences couldn't cope with British artillery in blue (because the Continentals all wore blue, didn't they?) and Loyalists in green (because.....well, just because, ok?). The guys charged with training up the extras created an entire British battalion, perfect in the 1764 Manual of Arms - at which point Emmerich arrived and said "Great! These guys can now disperse and cascade the information to all the new extras we're going to employ." He should have stuck to Godzilla.

And Gibson should have stuck to "Chicken Run" - probably the most/only historically accurate war film he has ever made.