Thanks to Mumbler Dad Chris for spotting this and sending me the idea!
Anti-flash white
When Vulcan XH558 was first delivered to RAF Waddington in 1960, it was painted in what was called ‘Anti-flash’ white. The reason for this design was to help reflect the heat from a nuclear blast. Download here
Camouflage
In 1964-1965, a number of Vulcan aircraft were chosen to be painted in two-tone green and grey disruptive camouflage markings to the upper surfaces. Vulcan XH558 was among them.
This colour scheme pattern would better aid the new role of the Vulcan in its lower level flying, to make it difficult for enemy fighters looking down on them to see them against the countryside, and when rising up, the lighter underbelly would be difficult to see from the ground and any visual targeting system. Download here