Peter, I totally agree with you on the shades if colour and how people remember them, however as my Father wasn,t even an itch in his dads pants when the Coronation was running I'm not in a position to remember it. What I have seen is a lot of black and white pictures which is no way to really judge the shade and a peice of film that was used in the T.V. series "Speed Machines" which shows the set some time I assume is later in it's life. Whilst the resolution isn't good enough to make out the locos number you can see that it is wearing the "economy" Garter Blue livery with no chrome/stainless trim and red and gold transfers, the set itself also seems to have had the roof painted dark grey or black.
Going back to the colours I've used verses the colours you've used, when I sprayed the first coach with Phoenix Marlborough Blue it looked too close to the Garter Blue of the Bachman A4 I'd just renumbered 4492 Dominion of New Zealand and I felt that I wasn't going to get the contrast between the two colours so of I went to find a shade that was a little lighter. Then I see the pictures that you posted here and the Marlborough Blue you used looks exactly the same as the Humbrol 65 I used, just out of interest does the colour look the same on your monitor as it does on your coaches? if so it must just have been a bad batch of paint that I had.