Queen Camilla wore black to meet Pope Francis at the Vatican, but why can Princess Charlene and other royal women wear white? All about the royal rule and fashion choices past.

King Charles and Queen Camilla paid a surprise visit to Pope Francis as he recuperates at the Vatican on Wednesday during a state visit to Italy that coincided with the British royal couple’s 20th wedding anniversary.

After being discharged from the hospital two weeks ago, Pope Francis held a private audience with the royal couple and shared his “best wishes” as they celebrate two decades of marriage.