I like the ancient blue, or a pair of diced ancient blue/black or ancient blue/charcoal hose if you want to go through the trouble of getting a custom pair made up. The Black and charcoal solid pipers hose would also look nice as you have mentioned.

I personally like to keep the red to my flashes with a kilt that has no red in it or only a small percentage of overall coloration as red. Just one man's O.