My husband's parents are what he calls "Puerto Rican supremacists". They did not approve of our courtship. His mother sent him phone numbers of "nice Puerto Rican girls" the whole time we were dating. His parents complained to him that I am ugly, and old. (I'm as attractive as most, and only four years older than he.) I saved his life once, and his parents told me tearfully that they were eternally grateful. They began treating me very kindly. Then he asked his father how he decided it was time to propose to his mother, and what kind of proposal it was, and they began dogging me again.
Now we're married. My husband has always made it clear to them that he loves me, and values me as a good person, a beautiful woman, and a best friend. He always rejected their manipulation. He told them that they raised him to look inside people for goodness, and to hold onto that goodness when he's found it. He told them they raised him not to judge on skin color. (And he pissed them off by asking them if they were aware that his surname is actually Arabic in origin, not Spanish, and that they are likely descended from Moors. He followed that up by asking them about certain family members having trouble with relationships, the law, and their unruly children.) He understands that he can't change them, but doesn't want them to change him, or us.
These days, his parents are very loving toward me, and consider me when we all have to make decisions as a family. They care about my feelings, and support my endeavors. I feel very good about this. However, the only thing I ever need from them, is that they love my children deeply, when I have some. My parents are dead, his are the only grandparents they'll get. I have never really cared too much how his parents feel about me, though I prefer we can love each other.
I think your significant other just has to be strong in their convictions and commitment, and you have to have a very thick skin. My In-laws are thousands of miles away. Distance helps.