Saw a picture of a B-17F in "A Storm of Eagles," a photo book that I got for Christmas. It was taken from directly above the aircraft, and showed 2 diagonal lines on the wings and 4 on the horizontal stabilizers. The caption stated that the lines were used as reference points for the waist gunners. Does anyone have any idea what color they were? The photo was black and white, and the lines contrasted sharply the olive drab, so I assume they were something bright (white, yellow, etc). I'd never seen this before.