I have two suits-- one is a standard issue black skirt suit, which is the most concervative and boring thing on the face of the earth, and the other one is gray (actually tiny black-white checker that looks gray unless you are 3 inches away). The gray one is more daring-- the jacket is knee-length and it has faux leather trimming along the cuff, colar, and waist line. It's still concervative, but it makes me look slightly different from everyone else without breaking the rules. So it depends-- the interviews where I felt I needed to fit in the most I have worn my black suit, and the interviews when I wanted to be more stylish, I went with the gray one.
Normally, I love colors and funky clothing designs, but I've been always tought that to be taken seriously in a professional setting it's important to go with the more serious colors and all that.
As for shoes... low heel is usually considered more serious and besides, it's more comfortable when you go on tours after/before the interviews.