I seem to remember that there was a third tart flavor last time I was there, besides orangeade and sno-bliz. Maybe it was Satsuma? I remember it being pretty good, too.
There's orangeade, lemonade, and limeade all on the same little sign (it's tiny and you have to really look for it). I'm not sure about satsuma, but someone mentioned it earlier as well (maybe Brennan?). Sounds interesting; I'll have to give that one a shot.