Not sure if both color backs were packed together. Currently, the sets are listed separately indicating separate releases. If the GREEN backs came in the same packs as the YELLOW backs then they should not be listed separately, but one as a parallel of the other.
The set title should be changed anyways. The fronts of the Classic Update are YELLOW, the only difference is the backs. Set titles should be changed to "1987 Classic Update" and "1987 Classic Update Green Backs".
Someday my cards may double in value and then be worth half of what I paid for them.