We used to require formals for Rituals but nowadays it's usually just a nice dress or even a nice pants suit. I've never had a Ritual where we required the pledge to wear a certain color. That might be a tradition of your new chapter but if so, it's a rare one. Church dress is usually the correct choice. Wear something you feel special in since this is your special time to shine! If you are in doubt feel free to call the chapter Vice President or President if you have their phone numbers, that's what they are there for. They'll be glad to know that you care enough to want to get it right. We tease the new pledges in our chapter and warn them to wear two pairs of clean underwear to the Ritual but we make it obvious we are joking, but most of us don't require anything special just that you come dressed in something that makes you proud and feel special and that you enjoy your special moment.