Oh man, I went through this same thing last winter and it drove me nuts. The trick is the cold oven gives you a slow rise which is great for the crumb, but you gotta crank the heat at the end to get any color on that crust. What I do now is start it cold, let it bake at like 350 for most of the time, then bump it to 450 for the last 15 minutes or so. You can also take the lid off your Dutch oven for that final stretch so the steam escapes and the outside can actually dry out and brown. If your crust is coming out pale and soft it basically means there was too much moisture hanging around the whole time. Try that and you should get a real crust without losing the nice inside.