Posted By:
Wesley"One note: If you happen to find one with an Old Put Stamp on the back in a color that isn't red or blue, than you've really got something."
The vast majority of the Old Put stamped cards are red. In fact, until very recently, it was believed that the stamp was only found on the red background E98s. I believe the one and only Old Put that is not on a red background card is Leon's blue background Clarke card.
As for the original question, Robert is dead on. None of the four colors for E98 cards are any more difficult than the other and collectors generally do not pay premiums for backgound color variations for E98s.