Conservative blue suit, black shoes and belt, red tie. End of discussion.

The interviewers were pretty funny about that stuff though. At the end of the interview they asked me I did any interview prep for the interview and I told them yes I did. Then they jokingly asked "you didn't get the memo about the red tie?" My tie was about half blue and half red. I went along with it saying I didn't realize that part of the interview portion was a sneaky color vision test. I told them I had to defend my tie decision as best I could saying there's a solid amount of red in there...at least 50% plus! They laughed about it and I got hired.