I think this concern with color is rather misplaced. if we are concerned with a riot situation, color of objects will hardly matter,nor will the view of a canteen cup through a semi-transparent cover influence anyone's actions.

As I have claimed before, the advice about "the grey man" is mythical and not corroborated by accounts of actual events (riots). As Chaosmagnet relates, the best course of action during a riot situation is to seek cover and/or exit the scene.

Of course, circumstances vary. During the Rodney King riots in LA, although reasonably distant, I checked my weapons and was reasonably ready, being responsible for Mrs. Hikermor, who is an excellent pistol shot, and our then infant daughter.

The vast majority of survival situations do not involve civil unrest or any kind of conflict. It is unrealistic and counter productive to focus undue attention on those rare situations.