This covers other makes too, but I’ve only scanned the Rootes Group pages.
Paint colours (text list, not paint chips) for Commer, Hillman, Humber, Singer and Sunbeam, by year. 1957, 1958, 1959, 1960, 1961, 1962, 1963, 1964, 1965, 1966.
Unfortunately it doesn’t list which combinations of colours were used for cars that had 2-tone paint, and neither does it list which paint colours went with the various upholstery colours. Brochures for each individual car are needed for that information.
Note that different colours may have been used in overseas markets.