Certainly no expert here, but...
I suspect that Sandi Steffner or Janice O'Neal might make the comment that there are three (3) different red variations for pips. It is not unusual for there to be color variations on the backs due to re-orders. Since may games today and going back for some years, involve multi-decks it is likely that the tedious process of re-packaging decks for giftshop sales did not take into account these shade differences, especially if done by an older male!
Bottom line, you have different partial decks and still need complete decks.
BTW-While I would like to have the entire set, I have found it to be very beneficial and informative to have several volumes of the playing card guides put out by Janice and Sandi. They include back variations and pip color variations.
Jim