Actually I think pastels were popular back in the 1970s I always see diesels painted that color along with a light beige, but it just represent the popular colors for the time. Along with the light blue and even signal red, I think all nonmetallic paints were pastels. As for the interior, it really messes up the combination. I'm not an artist but there is a clash between the red and the butterscotch and not in a good way. What color would fit that butterscotch and look decent? Maybe a light red, or light orange, or even a light beige parchment. Maybe either a black or brown interior would work, but that red is ugly, too bad the guy can't trade his interior for someone elses, the red would look nice in a white car.
If you had that car in colorado you probably wouldn't care what it looked like, especially after they salt the road.