[lampie]

Either way, it's an interesting photo/query but I don't think there's anything out of the ordinary here.

Exactly. No conspiracy theories in this case.

The victory markings on Gabbys plane were indeed stickers/decals which the man himself confirms in his book. These would have certainly reacted to the light in a different way to the paint on the aircraft itself.
As for Gabby ever dropping a bomb?
I have never seen a photo of Gabbys T'bolt with the underwing shackles fitted, so given that the only attachment point for a drop tank remaining is the centre fusalage shackles I think its very unlikely that he ever dropped ordnance.
Nige