At the first time Mike... It has something to do with the role-change of the Vulcan in the 60s. As it was clear that the Vulcan was not able "to overfly" the russian air-defence the next step was to equip the aircraft for low-level flight. They received Radar-Warning equipment and most Mk. 2 came with camouflage paint from the production line. Source: Avro Vulcan Britian's Supreme Cold War Warrior (Aerofax) from Phil Butler