Elementary School book read between 1962-1967.  A Prince from a kingdom where everyone has the same color of hair, climbs a mountain to the enemy kingdom where everyone has the same, but different color hair from the Valley Kingdom people.  He meets the Mountain Princess, and falls in love with her.  Together they must overcome the prejudice against different looking people that is held by their two kingdoms. Fairytale style color illustrations with simple narrative.  I think the Prince’s hair was brown and the Princess’ hair was silver.