Men
Dark, sober colours are always good and cotton wins over linen, even in the summer – linen creases ridiculously easily. Shoes should be brown or black – black with a black, grey or blue suit, brown with a brown or blue suit. Avoid mixing black and brown and always go for leather, not suede.
Similarly, avoid garish patterns on ties that can distract an interviewer. Ideally the tie will complement the whole ensemble, so it should be matched with the shirt as well as the suit. It's always easiest to go with a plain, white shirt and a non-patterned, single-coloured tie. Not one that features Captain America or Homer Simpson. The same applies to your socks and yes, the interviewer will notice.