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.
juan