Although I'm not greek I had to have a discussion with the girls in my dorm because at my PWI the white girls did not understand why they couldn't talk to the black girls who were pledging. It was an interesting because although the similar terms were used they were executed quite differently.
The whole rush experience was different - you have to visit every house-you (the interest) put in your bids and the various houses put in thier bids- if you are interested in going back (or if they want you to come back). After a couple of rounds and cuts its possible that you "match" with more than one house or with none at all. Once you agree to a final match then you receive your bid.
From what I remember - my (white)roommate said they could wear certain forms of their letters (such as spelled out - in this case Chi Omega) but they couldn't wear anything with the crest (since during the pledge period they didn't know what all the elements on the crest stood for) or with the actual greek letters. The rationale was they are members once they've gotten their bids-they just can't vote until they complete initiation. To them one can "depledge" if they chose/or are asked not to complete pledge process/initiation. So from my understanding they have two levels of membership-members who are pledging and members who have been initiated. They didn't understand that for Divine Nine groups you are not a member until you are fully initiated-thus no para (and don't leave any gifts in a pledge's room or at their door until they are finished-nice thought but definite trouble if a big sister came by).
Another thing - although they do each have official colors (I didn't realize this until my roommate) its not a big deal for them to wear their para with different colors. She just didn't get why you would never see an AKA wearing a blue/white sweater- or a Kappa with a purple/gold sweater. This was in the 80's - every semester we had to deal with trying to explain all the other "external" practices the Divine Nine were doing w/out saying too much (because obviously we really didn't know)...but had to say something so they wouldn't call campus police

.