As cool as those black-uniformed Cobra Troopers are in the Dollar General assortment, I decided that some sort of explanation for their uniform was needed. Thus I present the following "file card" for anyone interested.
COBRA DARK TROOPERSCobra Infantry
Cobra Dark Troopers are outfitted and trained like standard Cobra Troopers, but their uniforms are almost entirely black, with a silver Cobra emblem on the shirt. This is done largely for effect. The black uniforms appear more threatening and sinister, which enables a squad of Cobra Dark Troopers to take and maintain control over a populated area more effectively. It also enables the Cobra Dark Troopers to operate more readily in shadowy or night-time situations when more specialized troopers such as Night-Vipers or Alley-Vipers may not be immediately available. Although they're only a moderately specialized branch of the most basic Cobra infantry, they see themselves as the most "elite" of the Cobra infantry, doing the jobs that their more traditionally-uniformed counterparts can't, and that more highly-specialized Cobra troopers often won't.