Late in Season 1 when they switched to the '71 Satellite, they painted it in a yellow to match the original '73/4 Roadrunner. For the RR it had been a factory standard for that particular year, but apparently for continuity (and hoping the fans would not notice the change) they painted the new Satellite in the same shade of yellow as the Roadrunner. Thus it was a non-standard color for a '71 Plymouth of any sort.
After much research, and following an online discussion, the color seems to have been "Yellow Blaze." Fortunately Scalefinishes.com, who produces factory-matching colors for auto modelmakers, does carry this color...and when mine arrived I knew from the first glance that I had it right! Once sprayed I left it for over a week simply because I wanted it 100% cured before I began to handle it over and over and over.