Gilles, Zoran is right but the red 1st. Wing markings weren't marked up until the 2nd. week of July. This is Drawing 72518 / AC. The triangles were supposed to be black on the red but the 398th had several with reversed marking ie. white triangle outlined black, with black letter. Serials and a/c letter could be white or yellow ( occasionally black).
Nick
1st-bomb-wing by
Nicholas King, on Flickr