(Source One) "Reels made by GAF between 1978 to about 1981 are all subject to fading. They turn magenta, or look like they have a red tint. The date on the reel can be deceptive because the reel may have been reissued between those dates".
(Source Two) "Toward the end of the 1970s, and up to View-Master's sale to a group called View-Master International in 1981, GAF, the manufacturers of View-Master, stopped producing View-Master images on Kodachrome film and choose to use another type of film. Some have speculated that this film was Ektachrome while others believed that it was an Ansco film. Whichever film was used, it very soon lost its original vibrant color. The images have "color shifted" or "magentized".