So a few things....
1- I didn't know what a Lily Pulitzer was until I went through rush at UF. (or shall I say AFTER...)
2- The Lily Pulitzer dresses ARE cute... but I remember seeing girls wearing them as Round 3 dresses at UF, instead of Pref dresses.
Most girls wore black dresses to Pref... or something "prom-y" but without so much glitz and glamour. I saw everything from long dresses with dyed shoes to match, to short cocktail dresses. I wore a short red dress and red shoes... because I wanted to be remembered in the sea of black!
For rush... just wear what you're comfortable in. I'm sure my houses would not have changed if I had worn Lily all week long! (not to mention I would've looked silly!)