Re the cloth, blue or any other color, not so far as I know, but then I never claimed to know everything. As to mirage, it's caused by heat shimmer, off the ground, and the breeze tending to "move" the rising shimmer. The mirage, as I recall, would "blow away" with not all that much breeze. While rifle barrels get quite hot after not all that much fireing, I never noticed mirage off the barrel.