Posted By:
tbobI've collected all the E98s and nearly a master set (which is a snap compared to the E94)at one time but will address only the E94s which I am blindly buying trying to complete the master set (all 30 players in 6 colors=180 cards).
Brian mentioned gold variations and how I questioned their existence until I finally saw one of his and bought it. He's right, but actually he means an orange variation, not gold, as gold is one of the 6 colors in the set. I am sure that was just a slip of the keyboard. The orange variation is strange but my orange Devore rests in a PSA 6 holder now and it is definitely not red and definitely not gold. It could be considered a color freak except there are at least 4 others I have seen in the exact same color. All 5 came from Mr. Daniels originally, but I consider the master set complete at 180, with no orangies and no pinkies (as Brian mentioned), although I really would like to see a pink one, to see if it is just a faded red.
All of that out of the way, the numbers which are being mentioned above are not the finite number of cards known in each color, but rather Pete Calderon's survey of collectors he knew who had E94 cards. The numbers are certainly greater. They do, however, give an indication that gold and purple backgrounds are scarcer, in general, than the other four colors. On ebay recently there have been a run of 6 or 7 gold E94s but gold ones are still among the toughest.
Starting with the premise that ALL E94s are scarce as hen's teeth, I believe that there is something to the statement that certain players with certain colors are almost impossible, the scarcity of the gold and purples aside. I am 2/3 of the way home toward the master set and there are cards that I have never even seen, much less tried to buy and was outbid. For instance I had never seen a gold Wagner until the tattered one recently appeared on ebay and had never seen a gold Cobb until I saw Nagy's. I still have never seen a gold Young although as sure I say that, someone will post a scan of theirs 
Maybe this had something to do with the players pictured, I don't know. I do know that the toughest card to find, for me, is the Speaker. Why, I have no clue.
Finally, I think the most underrated color is olive, the ugliest color IMHO. They are tough to find and when you do find them, they tend to be in off condition, much more so than the other colors. I have no clue why. I know the survey indicated more of them around than other colors but in the last couple of years on ebay it seems like they come up infrequently, just like the purples.