Back in the day, we had Panhel shirts. Every sorority member who attended the rush kickoff event was supposed to wear one (instead of letters). Sorority members and female independent living group members then encouraged all unaffiliated women to attend orientation and then booked it back to their chapters to change into their open house outfits. Rho chis and deaffiliated Panhel officers wore these shirts for the remainder of the first day of rush.
During my freshman year, the shirts listed out the names of the five sororities on campus, with stick figures of 5 women, and the words "Feel the Rush". Cute idea, but these were the fugliest shirts ever - neon pink and yellow on navy - the shirts looked like someone had vomited on them. I flat out refused to buy one, and ended up borrowing one from my sorority for my sophomore year. (For some reason the sorority had laid in a couple of extra shirts.)
During my sophomore year, my sorority threw a monkey wrench into everything by going national. So Panhel had to redo the shirts. (I've been known to joke that we went national just so we could get decent-looking Panhel shirts.
) During my junior year, they went with a "world travel" theme. The shirts had a front pocket design reading "United Sisters of _____" and a listing of all the sororities on the back. Navy shirts, white printing. That one, I bought. As far as I know, those shirts remained in use until Pi Phi colonized a few years ago.
(BTW, the shirts had to have the names of the sororities spelled out, as my school has chapters of Kappa Alpha Theta and Alpha Epsilon Phi, and these sororities do not allow anyone other than initiated sisters to wear their respective Greek letters. Just something to keep in mind.)
Hope this helps.