RE: Tips on the US National Insignia
The next thing we must add; unless we’re modeling some 15th Air Force aircraft, is the surround that borders the whole insignia. As we learned this was intended to be red, but by 14 August 1943; just over 2 months after the red surround was directed, folks in the pacific theater determined that red was too risky and labor intensive to apply.
Roughly two months later the border was changed to be the same color as the blue background behind the star. The key characteristic though was the width of the surround. This was often done incorrectly on the full size just as it is on models.