Black

Black was a colour.

The Master usually dressed in all-black clothes. (TV: Terror of the Autons et al.) The Trickster normally wore a long black hooded robe and gloves. (TV: Whatever Happened to Sarah Jane? et al.)

The Host of the Lupine Wavelength Haemovariform had all-black eyes. (TV: Tooth and Claw) Mercy Hartigan's eyes turned all-black when she was converted into the CyberKing. (TV: The Next Doctor) Owen Harper's eyes turned all-black when he was possessed by Death. (TV: Dead Man Walking)

Nostrovites had black blood (TV: Something Borrowed), as did the Process. (PROSE: Cat's Cradle: Time's Crucible)