While you may get the desired flavor out of fresh herbs, your presentation will suffer. No one wants to eat black, limp oregano, basil, rosemary or other herbs.
If you're steeping stock or simmering sauce, dried herbs are the better choice. They'll have plenty of time for the heat in the liquid of the dish to break them down and the color loss will be insignificant. You may, however, want to have some of the fresh varieties ready and chopped for the final presentation.
One more note: when herbs are dried, their oils are trapped inside the herb. Since almost all the flavor of the herb is in its oils, shake the dried herb into the palm of your hand first, then pinch and CRUSH it with your fingers before sprinkling it into your dish. This will allow more of the oils to escape since you will break apart that outer, dried crust of the herb.