Pekka, yes you are correct in 1945 to Nov 1952 when Jaguar was using British Domolac cellulose based paints, the only ‘white’ colour offered was called IVORY (for marketing purposes/brochures etc), and indeed also more correctly technically by British Domolac who called this colour IVORY code X.6427, so the code was what mattered, defining exact shade of white by a repeatable paint formula.
From Nov 1952 onwards, thus later XK120s/Mark VIIs Jaguar changed to a totally new supplier Pinchin Johnson, of the latest improved SYNTHETIC ENAMELS and indeed from a Marketing perspective the sole ‘white’ colour available was now referred to as being CREAM, albeit technically for accuracy the paint manufacturer called this colour OLD ENGLISH WHITE J.863 (the J denoting special shade for Jaguar). Now you have to wonder why the Marketing people changed from IVORY to CREAM, given that to most casual observers the shade of white was very similar, if not to most the same, so I suspect more a case of concerns of paint touch ups, not mixing Synthetic Enamel and Cellulose enamels. Interestingly in Australia, post 1952, Brylaws (HQ in Melbourne) referred to CREAM, and major Dealership Brylaws (in Sydney) referred to IVORY still…
If you go back to prewar, when SS Jaguar offered one only ‘white’ colour in their standard range, for marketing and technical code accuracy for 1938-9MY they offered IVORY code D.7267 - as made/supplied by British Domolac, but in 1937-8MY the one only ‘white’ colour offered was CREAM code D.1267.
So was D.7267 a typo, or maybe some minor chemistry/shade change from D.1267, and how good a match was the Mark IV/V IVORY X.6427
As far as 640092 was concerned, it was of course originally restored/repainted in 1982, and then called CREAM, but who knows exactly what paint was then used, and how accurate or otherwise was the colour match to the original IVORY Cellulose Enamel…
As we all know colour matching is far from an exact science, and we have all seen rows of Jaguars all different shades of say GREEN or in this case WHITE, all claiming to be correct factory BRG or IVORY/CREAM/OLD ENGLISH WHITE - before we concern ourselves with all the MGs and Aston Martins etc also claiming to be BRG, although not originally the same shade Green as Jaguar anyway…