Pink
From Tardis Wiki, the free Doctor Who reference
Pink was a colour.
The Zero Room was pink. (TV: Castrovalva)
The Happiness Patrol painted the Doctor's TARDIS pink. (TV: The Happiness Patrol)
Kalarians and Ukkans had light pink skin. (PROSE: The Final Sanction, TV: Lost Library of Ukko)
In the Mulifane system, pink was the traditional colour of fighting. (AUDIO: Forgotten Lives)
The snow on Nirvana was pink. (AUDIO: World Apart)