If you want to match the jacket, the Scottish Tartans Museuem offers charcoal and grey hose in the Lewis line.

http://giftshop.scottishtartans.org/hose_lewis.htm

Personally, I wear Lovat green hose to match the green in my kilt when wearing a charcoal grey jacket. Also, in agreement with Jock, if it looks good wear it. I'll cite the Duke of Argyll, who wears red hose with his Ancient Campbell tartan kilt. Quite dashing in my opinion.