For an office worker I'd say go for a dark self colour with a matching jacket, tie and socks, and a plain sporran. Dealing with the public in formal circumstances, I wear a black heavyweight for court duty. I wear the regulation long black robe over it while in court; the robe is open at the front therefore it is obvious to all present that I am wearing a kilt. I think being greeted by a kilted official helps put the public at ease as attending court can be stressful. For a tourist related activity, such as museum guide, where you are meeting the public in happier circumstances, then I'd opt for a tartan.