An insider at Paramount claims that from 1997 onwards, the colours on The Godfather and Part II have never been correct and very likely, never will be. A depressing read that also includes details of how the original negative was mishandled during the 80s for home video transfers.
http://godfathermuseum.blogspot.co.uk/2015/03/screen-shots-and-technical-errata.html
Man, I never would have known. The Coppola restorations of the first two are top notch releases that look phenomenal.