Privilège du blanc
Appearance
White privilege, or Privilege du blanc, is a privilege held by Catholic queens and the Grand Duchess of Luxembourg wherein they are allowed to wear white when in an audience with the Pope. Protocol for papal audiences required long-sleeved, formal black garments and a black veil for women.
Currently, only the Queens of Spain, Belgium and the Grand Duchess of Luxembourg. Reigning princesses or princess consorts do not hold this privilege. HRH Princess Grace of Monaco had to wear black when she met the Pope.
See also Catholic King, Catholic monarchs