Aliens: Colonial Marines is a squad-based first-person shooter in which the player controls four Colonial Marines, each with a different personality and primary weapon. Each player character can carry additional weapons including a flamethrower, pulse rifle, smartgun, pistol, RPG, and many types of grenades. The player controls one marine at a time, issues orders to the others using context-sensitive commands, and may switch between characters at any time.
Simply recolours the underslung shotgun for the Pulse Rifle, so it matches the finish of the weapon. Always bugged me how both grenade launchers matched the base weapon but the shotgun contrasted so badly :P Before/After example in screenshot.