I ditto black - generally the "rule" is that your legs and shoes should not be lighter than your skirt. So...that would lean toward black. That said, you could do something fun other than plain 'ol black with the "decorative" stockings (not fishnets per se, but they have some cool, tasteful lace-ish ones that would be fun and dressupy.)
I say anything that is comfortable. We just went to christmas office party and it was the first time I decided to wear dress pants instead of a dress. WOwsers. But I was comfy and warm :)
Have fun at the party though!!
(Just HAD to throw something else into the mix, didn't I.....)
Black is fine for a party - really. Just take an extra pair in case of a run, and have a great time!!
But plain is good too!