If I only had one kilt and could only have one pair of hose, then matching tartan without question. However, that is not a very economical option.

In terms of frequency of wear, dark/bottle green gets worn more than any other colour. It works with all of my kilts and given the prominance of green in so many tartans, it makes a good universal choice. Black is a good default as well and works for both day and evening wear. There is a good reason why so many pipe bands wear black hose.

I have a pair of off-white hose in the bottom of a drawer somewhere. Can't remember the last time they were worn. However, don't care to get between Jock Scot and CDNSushi on this one.