Moth Eaten, For what its worth, I have been told (on good authority), that some of the old tinters are no longer used because of toxicity and other issues so old colours can no longer be accurately reproduced using the old formulae. Modern mixes may be close but not necessarily "spot-ob".
I have completed much research over the years and more recently with Terry Andrews and Tommmm in the USA.
There are various posts in archives on this forum relating to colours.
A large number of prewar colours were brought forward by MG into the T series and again into the MGB range with colour name changes and are as far as my old colour chips books show, a very close match.
The Glasurit brand of two pack paint has most colours reformulated to use modern tinters, Dupont has some also.
The colours had a British Standard prefix ie GN for green RD for red. YL for yellow and ivory, BU for blue, GR for grey.
I have an old document that I wrote some years ago that I should update and see if the Bulletin or Year Book editors want to publish it.