When I was an active (fall 01-spring 05) we were really strict about rush clothing. Typically it went like this:
Go Greek/16-party day: Panhel issued t-shirts, every house got tshirts in a certain color with their letters on the front and a design on the back, which listed all the sororities and usually had a cute saying of some kind. Competition over colors was usually fierce since Panhel randomly picked 13 colors and then each house would draw a number to decide what order they picked their shirt color. Pink was always chosen first and the ugly colors like moss green (which we unfortunately had my junior. year

) were the last to go. My senior year we had light pink shirts with hot pink writing, LOVED those! And last year when I helped as an alum (2005 recruitment) they had black with hot pink/magenta-ish writing, also cute! Each house then decided on what they would wear on the bottom, usually a denim, khaki, or white skirt. My house bulk ordered whatever we chose from places like American Eagle, Gap, Old Navy, etc. to make sure we all matched. We also bulk ordered Phi Mu flip flops, or another type of flip-flop to wear.
Skit/9-Party Day: For this day we wore black and white outfits with a hot pink accessory, such as earrings, a belt, a scarf, etc. The outfits were to be dressy, like nice capri pants and a nice top, or a nice dress. Also had to wear black heels on this day. People in the skit obviously wore their costumes.
House tours/Philanthropy/5-Party Day: The theme for this day was (and still is) "Phi Mu of the Caribbean" and we all wore the same t-shirt that the day chair had designed. My favorite year was when they were bright blue with a picture of an island with palm trees on the back which said "We went looking for treasure and found Phi Mu!" and said "Phi Mu of the Caribbean" on the front. We wore those with light khaki American Eagle skirts (bulk ordered again) and bright blue J Crew flip flops that were the exact same shade as the shirt. That was my junior year, senior year we switched to red tshirts with black writing and wore black capri pants and black flip-flops.
Pref Day: For the first two years while I was active we all had to wear the EXACT SAME BLACK DRESS. It was a nightmare. They were so ugly and uncomfortable, not to mention expensive after I got mine tailored to actually fit. We also had to wear the exact same black heels as one another, plus pearls or our lavaliers and our badges. The shoes were open-toed so that meant no nailpolish except something extremely light and not noticeable. We looked like clones, not cool at all. Finally my senior year we were allowed to wear "approved" black cocktail dresses and our own black heels. I chose this year to wear a really cute pair of black, strappy Steve Madden shoes that had a silver ring on the top (hard to explain but they were cute). SUCH A BAD IDEA. After standing on the front porch in 90 degree heat, sun blazing down on me all day, that stupid silver ring burned into my foot. I still have faint scars from that, so awful.
BID DAY: We all wore our bid day tshirts which were exactly like the new Phi's shirts, except ours were different colored. Theirs usually got to be pink

, while ours were white, black, or whatever color (light blue one year, eww). We wore these with denim skirts, of our own choice, and the black Phi Mu flip flops we all had.
Our recruitment, as you can tell, was pretty strict while I was active. I know now they're getting away from that so people can be more "themselves" but I didn't ever really mind getting the stuff. We would always bulk order skirts, tshirts, and shoes (flip flops, heels, and even matching tennis shoes one year!

) because when there are 170+ girls in your house you can't really count on being able to show people what they should get and expecting everyone to come back with things that all looked at least somewhat similar, or at least "meshed well" together. Even though it might seem extreme to some people, it was really the only way to make sure we didn't look like a big jumbled mess. Slightly different outfits, or denim color, or skirt colors, or whatever can look cute when there are 20 or 30 of you. But when there are so many girls, plus alums (who also dressed like us), 200 people in 200 different outfits looks kind of sloppy.
Ok, sorry this was way too long and probably boring, I'm done now!