Patriotic- Red white and blue would work for me. (Like the Union Jack of course. Other flags in the same colours are available.
Commissar's Red and Black would look spiffing too- especially on a blacked out blade/hardware.
Warhammer 40000 is- basically- Lord Of The Rings on a cocktail of every drug known to man and genuine lunar dust, stuck in a blender with Alien, Mechwarrior, Dune, Starship Troopers, Fahrenheit 451 and Star Wars, bathed in blood, turned up to eleventy billion, set on fire, and catapulted off into space screaming "WAAAGH!" and waving a chainsaw sword- without the happy ending.