Regardless of anything, it's perfectly fine to do (in a well ventilated room or even outside) while pregnant 😊 I make one of my friends do it for me because it hurts my arms so you can use that excuse too 😉
The color of your hair? Naturally? Not that I know of :/ you can use box stripper but it kills hair. So that sucks. But it's not necessarily "bad" just because you're pregnant 😊
If you want to lighten it, you can try lemon and water in a spray bottle and spray it EVENLY Through your hair, it'll take a couple weeks but it does work