What color should we get our room painted?

My mom and her fiance are getting married, and he has a daughter that I now have to share a room with (yikes..) My future step sister wants to paint the room black, but her dad said no. I wanted to paint it a pastel color, but then again I want the room to pop and I really like prints, but I don't want to control everything by painting what I want, even though she said she doesn't care. We're both the same age, if that makes any difference..lol. Help?