Corrected entry: During the library scene, Violet has custom guns with purple muzzle flares. The shape of these flares are Biohazard symbols, a direct reference to Resident Evil, one of Jovovich's earlier movies. Resident Evil is known as Biohazard in Japan, the origin of the series.
Friso94
5th Sep 2011
Correction: Seems kind of a reach. Unless there's some commentary on the issue by someone involved with the production of the film (and if there is, it ought to be cited in the entry) I'd say it's much more likely they're biohazard symbols because that's a "cool" shape for the flares to take.
Phixius ★