I waterfowl hunted for many years, and because of the location and how we had to orient our blind we were staring at the sunrise. Obviously, a bare face would look like a spotlight glowing. We always used either a face mask or painted our face to stop that issue, and we always had the barrel of the gun propped and sticking out of the blind. To my knowledge not once over all those years did we have ducks or geese flare because they were spooked by the shiny blue barrels of our shotguns.
If it makes someone feel better, then by all means camo everything in use. But I personally don't see the point if motion is avoided and the wind is taken into consideration. Especially if a call or/and a motion decoy is in use to direct the attention away from the shooter.