I stand corrected, I zoomed in and saw the 6. Kind of a grayish looking green, but it seems that BD has about 20 colors of green. Agreed that I don't know where you would put a 6 in, maybe up high?, but it would be hard to get this photo from up there (?).
The fact that it's the size of the climber's head also betrays it as a #6. Not sure where he stuck it either. This is a fist crack. Perhaps he was just nurturing that urge to pose for the ol' "Look Ma, Big Cam" picture.