Complex sentence: Mary, Queen of Scots, wore a white wedding gown in 1559 when she married her first husband, Francis Dauphin of France because it was her favorite color, although white was then the color of mourning for French Queens.
Split into simpler sentences: Mary, Queen of Scots, wore a white wedding gown when she married her first husband, Francis Dauphin of France in 1559. She chose to wear a white gown because it was her favorite color, although at the time white was the color of mourning for French Queens.