At FSU it's very casual for both Greeks and non-Greeks. You definitely wouldn't be able to tell whether or not someone was affiliated with a GLO just by what they were wearing. Granted, there's block seating for fraternities and sororities at the games, but you would look strange if you showed up to an FSU game all dressed up. "Cute" attire for girls is shorts or jeans and a cute top.
I grew up in Auburn and going to many Auburn football games, so I am familiar with the usual Greek dress there. And yes, even as a spectator outside of that particular Greek system, it DOES stand out and does look classy. Sometimes it seems a bit ridiculous to go to a football game all dressed up...but it IS the south and we tend to "over do" everything here