Having consulted many men on this very question, my advice is to wear a pair of black plain toed oxfords. A dark brown can be worn, but it is complimented better by a lighter suit and is less formal than the same shoe in black. Another option is black straight tip blucher oxfords. Your shoes are the foundation of your outfit, and for an interview should be a pair of a certain degree of formality – no slip-ons, no boots, nothing that draws attention to itself. And by all means, ensure the shoes are shined and free of marks.
It was mentioned above that no one notices or cares what you wear: nothing could be further from the truth. The shoes and clothing that you wear is VERY important; the interviewer’s first impression of you will be made within 3 seconds. Clothing covers 90% of our bodies, and sends a message before we even have the chance to open our mouths. Countless communication studies show that a clean & friendly appearance creates positive emotions; certain colors create feelings such as trust and authority. Every person who wants to be taken seriously in an interview should make sure their clothes fit them, compliment their body type, and are timeless in style (thus never out of fashion). Because the interviewers are going to ask themselves “Is this someone we want representing us?”
You are spending a lot of money on your education. Don’t blow it in the interview by wearing a cheap suit that doesn’t fit and bad shoes.