When I wear a tie (which doesn't happen a lot), I like to wear a solid color that matches the dominant color of the kilt. Below shows a red tie with the MacIan tartan kilt and a lovat blue/grey tie with the Edwards tartan kilt:





I have to agree with Matt about the tartan bow tie above. With the formal outfit, the tartan tie looks too informal to me. However, I think that would be a great tie to go with a tweed jacket and that kilt.