Im looking for an anime i read a long time ago where the herorine has red hair?

It dealt with a kingdom where the color of your hair was how royal your family is. The blacker the hair the more royal you were. In the manga the girl whose a princess from the next kingdom is married off to the prince of the other kingdom in a way to stop the war. Because her hair is red shes outcasted even in her own kingdom. The prince she's married off to has black hair and is cruel but gradually the two begin to fall in love with each other.