You're right Sarah, what that person said to you was wrong. Whether they meant it in a mean way or not I cannot tell because I wasn't there.
If this was Building Access Staff (BAS) or a CA you should go straight to your Res Manager, you can get that persons information off the Housing Website this is the
RM listing. The listing is old... sorry I can't find the newer information but the building extentions should be the same, it just might not be the person that it says on that website, or you can always call the office and ask for the RM of your building. Set up an appointment and talk to the RM, explain the situation and how you felt. They will deal with it and keep you up to date about it.
If the person was a student, go talk to your CA, it will probably end up with the RM anyway but talk to your CA first
As for a repeat experience: I personally would confront the person if they do it again. We as Canadians are so quick to tell everyone that we are multi-cultured but so many of us do not truly appreciate it. Call him/her out on it infront of everyone else and tell that person that you shouldn't have to descriminated against because of how you are dressed. You do not have to tolerate racist comments, ever.