Carnage, In most cases the pylon is a separate entity from the aircraft. That is, it will have it's own serial number. if it does (check photo's) then from time to time it will be removed for servicing, which could include a repaint. Some aircraft have permanently attached pylons, in which case the colour probably would be the same as the aircraft.
I've found that the ordnance is better fixed on with a short length of wire.
Drill into the pylon & bomb or whatever, and superglue thin wire into the holes to get a good permanent joint. It means you have to be accurate when drilling to get things lined up, but the bombs won't fall off with handling or over time.
Pete