From what I've heard from people who interview students, it is helpful if you have a stand out piece of clothing for people to remember you by. I certainly don't mean a neon yellow pantsuit, but a nice pop of color somewhere can let professors (mainly who aren't your PI of interest) who speak with you out of maybe 20 others that day say "Ah! Pink necklace girl. I liked her!" rather than "mmm I don't remember her." Some places take head shots to help them remember who was who during discussions post-interview, but not all, so something else identifiable can help!