We do dress check for every round of rush as well as for our formals. That's just how it is down South.
And for our prefs, we wear black cocktail dresses-- no strapless or spaghetti strap-- black closed-toe dress shoes, nude hose, pearls, our badge, and we follow the 3-piece jewelry rule-- no more than 3 pieces of jewelry on, including your pearls.
I also thought that Gamma Phi encouraged all of its chapters to wear black at pref, but who knows.
Classy, ladies, classy.