You can buy grout paint and paint it any color you want. But, in my experience, no matter what color you start with, grout turns grey/brown. Not worth the effort of trying to change it, unless you are going to seal it.
Standing up to her, if she is a bully, is essential. However, in a happy marriage, the partners are not confrontational, they negotiate. They ask each others' opinion and try to come to consensus on things. So standing up may be a 180, and it will change the routine, but it doesn't get you all the way to happy.
