Black pants with White jacket - What tie?

If the tie is around 60% black (2/5ths up the darkness line in the Microsoft More Colours/Custom), then that's great. Otherwise, find something in a solid slightly dark red or blue, and wear that, so that it gives colour to the rest of the outfit. Not too light a colour (maybe anything 50-80% black for a blue and 60-80% black for a red), and shiny, should look great.