Pantihose, Skivvies, and Slips, Oh My!
To determine hosiery color "from scratch", I use the length-balancing principles I explained here, in How to Wear a High Waisted Skirt. For abundant specifics on this topic, and more, Ask Alison.
Skivvies, aka thermals or long underwear, are a winter necessity here in the mountains of the Great Northwest, much warmer and more comfortable than nylon stockings. I wear these daily. Under jeans, of course.
With skirts and dresses, I dodge the need for a slip with an old-school style-enhancing feature: LINING. Frankly, and I own this as a strong personal preference, slips just don't work well. How many otherwise well-dressed women ruin their entire look with a slipping slip? If it doesn't have a lining, I just wait to wear it until the weather's warm enough to go stocking-free.
Slightly related, Jenn and I were talking in comments over here about socks (context: not looking dated). What kind do you wear?