It's even more complicated.
There are two separate foiled areas that were applied independently, meaning that the cards can be identical in one area but different in the other.
The upper foiled area is the Stadium Club logo. The lower foiled area is the Extreme Corps name and a diagonal bar.
The cards can be found with rainbow foil at the bottom or red foil. When it has rainbow foil, it can go in forward (ROYGBIV) or reverse (VIBGYOR) order.
Rainbow foil bottoms can be found with rainbow foil tops or solid color foil tops, but the solid color is an artifact of printing, because the three solid colors that can be found are red, yellow, and blue, which are the widest color bands in the foil (the upper foiled area is much smaller than the lower foiled area).
Red foil bottoms are only found with red foil tops.
Rainbow foil appears to be somewhat morecommon than red foil, but this may be a result of which ones people choose to keep or sell.
Due to the wide variety of gradations among colors, the most I will do to recognize and catalogue variations in my collection is to distinguish red and rainbow foil cards. I expect that only the most diehard player collectors or extreme completist will pursue it further.
PSA, COMC, Beckett, etc. do not recognize these as variations at all, which I expect has led most collectors to follow suit.