I am not really sure that different colours were used. From what I recall seeing, when any of the class were on the ship lift, the apparent colour differences were caused more by light reflecting of the different materials with which the ships were covered than actual paint shades used. Some materials had a very matt finish whilst others had a bit os a sheen to them. This photo, of HMS Astute, may illustrate what I mean as I believe it would have been finished in the same way.
Hope this does not make things harder for you.
Dave Ross (from Barrow, where Vanguard was built)