I think blonde hair and blue eyes are aesthetically much more attractive, and for that reason I do not want to "mix" when I get married--because I want to pass my blonde hair and blue eyes onto my children.
Blue eyes and blond hair are signs of youth, and when humans migrated into the cold regions of Northern Europe and had to bundle up tightly, women had to conceal their tits and curves. So they evolved other ways to broadcast their youth and health: their faces. So northern women now retain blue eyes and blond hair longer.