(Almost) all of them might come in 3 versions: unmarbled, slightly marbled or heavily marbled (with 1 color or with multiple colors). Another type of distinction: see-through vinyl or non-see-through vinyl.
Just my 2 cents on this subject (while I’m no vinyl collector, ahem…).
Update, I forgot pink…
Billy Corgan, December 2, 2008 : "Not everyone understands our death trip. But you do. And that's what matters."