Royal purple was a a deep reddish-purple colour, sometimes approaching a strong violet; connected to royalty.
Donna Noble wore a royal purple stola when facing Pyrovile in Pompeii during 79, (TV: The Fires of Pompeii) and when helping to defy Darac-Poul-Caparrel-Jal-7 and some Gelem warriors in Calcutta during 1947. (PROSE: Ghosts of India)