The saturation is due to flare or the absence of it, an extremely well Multi-coated lens will give the best saturation.

Early coatings often tended to be rather cold (in colour terms0 and give a bluish tinge hence the warm up filters that most people used in the 1960's and early 1970's. Some lens coatings were decidedly strong I have a CZJ 150mm Tessar from the early 1950's that gives a distinct blue cast but by the late 1960's the coatings on many German LF lenses (Schneider & Rodsenstock) were close to later MC versions and extremely good.

The term Single coated is a bit of a minomer because often lenses had more than one coating, but these were applied individually. CZJ were using more than one layer by WWII for some applications.

The best lenses are multi coated on eveery glass/air surface but one major lens manufacturer had to scrap their entire range and drop their brand name from lenses after a disasterous series of poorly coated lenses went on sale, suprisingly that was Hoya. Hoya and Tokina have common ownership and a completely new redesigned range of lenses was released under the Tokina brand name

Ian