[x2drich2000]

Originally Posted by nolemmings

Here's a link to the Old Cardboard checklist (an invaluable site IMO):
https://www.oldcardboard.com/m/m116/m116SearchIndex.asp
"Blue back" is a reference to the advertising on the back, as the cards can be found with either in blue or black print.

To expand on Todd's comment a little bit, the backs of the cards come with several different variations including some printed in blue and black color print. If you look at Leon's image in the post above as an example, both the Conroy and Moren have the same text back, but in different colors. Young can be found with both black and blue printed backs, but is only found with the pastel background on the front of the card. Meanwhile, some players like Wagner can be found with both a pastel and blue background on the front of the card, but only blue printed backs.