Scarlet

Members of the Prydonian Chapter were distinguished from the other Chapters by their scarlet and orange robes. (TV: The Deadly Assassin)

Gwen Cooper wore a scarlet shirt throughout the 21st century Dalek invasion. (TV: The Stolen Earth, Journey's End)

Ace wore a scarlet t-shirt during her encounter with the Master and the Cheetah People. (TV: Survival)