Scarlet

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

It was also the colour of a shirt worn by Gwen Cooper throughout the 21st century Dalek invasion. (TV: The Stolen Earth, Journey's End)

The Seventh Doctor wore a single breast waistcoat of scarlet brocade up to his death. (TV: Doctor Who)

The Master wore a scarlet t-shirt. (TV: The End of Time)