I never saw a 1-hour photo place until the early 80s. The change
I see in the prints began about a decade earlier - in the early
70s - so I don't believe the 1-hour process is the culprit.  The
bad color seems to begin at about the time they began using that
awful "satin finish" paper. It was a rough surface paper - used,
I believe to help hide grain and other distortions from cheap
cameras with cheap lenses and tiny negatives. This was the
period of the 110 Pocket Instamatic camera, which I believe was
introduced in 1972.  But again, what is stunning is the quality
of the color from the late 50s and early 60s.