Nothing says "fresh start" like a new hair hue, but it's all too easy to run into trouble when you're dyeing. Keep the shade in the same family as your skin's undertones — in other words, if you've got warm undertones, make sure your shade is as well. The other rule is that you shouldn't go more than two shades lighter or darker than your natural hair color (although I'm not a big believer in rules). If you are going drastically lighter or darker, I suggest going to a stylist, though, at least for your first attempt.
The Transformative Hair Color