Here's a relatively simple approach to mixing colors: select two colors as the primary ones for your outfit, then use the shade that results from mixing the two primary colors together as your accent. Here I've chosen blue and green as my two primary colors, and blue-green, or teal, as my accent. The accent color compliments both of the primaries equally, while providing more interest to the outfit and keeping it from being too matchy. In this case, the teal color also made the look a little more seasonally-appropriate, since it brightened up the otherwise subdued color scheme of the outfit.
Lately I seem to have gotten over my previous aversion to letting the tops of my socks show. I guess I always considered the look to be too school-girlish, but I've found that wearing shorter socks instead of tights or thigh highs is a great way to keep your feet warm while still bearing some leg in the supposedly warmer months (I say supposedly because San Francisco isn't very warm at all in the spring or even summer, and yet we're still expected to dress as if it is). Surprisingly, these mid-calf socks had no trouble staying up all day with no extra tugging or adjustment needed. Since most of my sock collection is comprised of above-the-knees and thigh highs, I think an order to Sock Dreams may be in my near future.
Socks: Sock Dreams
Shoes: John Fluevog