I think you are getting solid advice from the replies. Conservative is the the bottom line. I heard a story from a friend at UPS about a class of potentials turning up...all had the blue or gray suit etc. One guy decided to impress the big brown by wearing a brown suit, shoes etc...show the company colors.
All in that interview session got hired, but one...you guessed it...the guy in brown.
There are interview prep people that you can go to...will give you advice on your suit aswell as the normal prep questions.