I never knew that. But I always thought the base colour of "Blue John", judging solely by the illustrations on subsequent BJP LPs, would be a bit nearer to the blue on "The way I feel". I was a bit disappointed when I got the LP in '85 or '86, whenever it was.
MG
Additional problems arose because most BN covers were not 4 color process but printed to Pantone color numbers or custom ink blends. By the time these films were used the industry had move to "process" as the standard and everything had to be converted.