Black

Black was a colour.

Clothing

The Master usually dressed in mostly black clothes. (TV: Terror of the Autons, Frontier in Space, The Deadly Assassin, The Keeper of Traken, Doctor Who, Utopia, Last of the Time Lords, The End of Time, The Doctor Falls, Spyfall)

Davros wore a black lab tunic. (TV: Genesis of the Daleks, Destiny of the Daleks, Resurrection of the Daleks, Revelation of the Daleks, Remembrance of the Daleks, The Stolen Earth, Journey's End, The Magician's Apprentice, The Witch's Familiar; AUDIO: The Juggernauts, et al.)

Black Daleks were identified by their black casings. (COMIC: Duel of the Daleks, TV: The Dalek Invasion of Earth, The Chase, The Dalek's Master Plan, Resurrection of the Daleks, Remembrance of the Daleks, AUDIO: The Juggernauts, Brotherhood of the Daleks, The Apocalypse Element, et al.) Dalek Sec had a completely black casing. (PROSE: Birth of a Legend, TV: Army of Ghosts/Doomsday, Daleks in Manhattan/Evolution of the Daleks)

Cyber Leaders were identified by their black head handlebars. (TV: Earthshock, The Five Doctors, Attack of the Cybermen, Silver Nemesis, Army of Ghosts/Doomsday, The Pandorica Opens, et al.)

The Voord wore black bodysuits. (TV: The Keys of Marinus)

The Trickster normally wore a long black hooded robe and gloves. (TV: Whatever Happened to Sarah Jane?, The Temptation of Sarah Jane Smith, The Wedding of Sarah Jane Smith)

The Ninth Doctor normally wore all black articles of clothing, save for a long sleeve jumper of a different colour, (TV: Rose et al.) though by the end of his life even the jumper he wore was black. (TV: Bad Wolf/The Parting of the Ways)

The First Doctor wore a black town coat. (TV: An Unearthly Child, The Daleks, Marco Polo, The Dalek Invasion of Earth, The Chase, The Dalek's Master Plan, The Tenth Planet, The Three Doctors, The Five Doctors, Twice Upon A Time et al.)

The War Doctor wore a double-breast leather trenchcoat done in black. (COMIC: The Whole Thing's Bananas)

The Eleventh Doctor once wore a black moleskin overcoat. (TV: A Town Called Mercy)

The Twelfth Doctor often wore a black velvet frockcoat. (TV: The Pilot, Thin Ice.)

Martha Jones wore black bodysuits. (TV: Last of the Time Lords, The Sontaran Stratagem, The Stolen Earth|Journey's End, The End of Time). She also wore a black top with a v-neck collar. (TV: The Sontaran Stratagem) which was then worn by her clone posing as her. (TV: The Poison Sky)

When attending Daniel Barton's birthday party at the Vallis Estate vineyard, the Thirteenth Doctor, Yasmin Khan, Ryan Sinclair and Graham O'Brien all wore black tuxedoes and bow ties. (TV: Spyfall)

Clara Oswald wore a black leather jacket on occasion. (TV: The Magician's Apprentice/The Witch's Familiar)

Rose Tyler's personal growth during her travels with the Doctor began to reflect itself in her clothing choices as she became more confident and assertive, swapping her jeans for slim black trousers. (TV: The Long Game, Bad Wolf/The Parting of the Ways, New Earth, Fear Her, Army of Ghosts/Doomsday, The Stolen Earth|Journey's End)

On her first day on the job working for Torchwood, Gwen Cooper wore a black blouse. (TV: Day One) During her time with Torchwood Three, she would favour an increasingly black and leather wardrobe.

During Torchwood Three's confrontation with a cyber-converted Lisa Hallett, Toshiko Sato wore a black t-shirt. (TV: Cyberwoman)

Sarah Jane Smith often wore a black leather jacket. (TV: The Monster of Peladon, School Reunion)

Romana wore a black ribbon tie. (TV: State of Decay)

Some individuals wore black lipstick. (PROSE: No Future, Goth Opera, Dry Pilgrimage)

In Through the Eye of Eternity, the Black Eye of Eternity generally symbolised that the week's episode would be a black comedy. One fan wearing a black Eye pin, an apprentice mortician in Shoestring, Indiana, was fired after laughing at a client's sombre remark. (PROSE: The Book of the War)

In an alternate timeline in which the First Doctor spent three months on Urbinia, his friend, Professor Feedlam discovered a new colour which was "a little bit green and a little bit black", creating "a sort of mauve". (AUDIO: Daughter of the Gods)

Biology

The Second Doctor had black hair. (TV: The Tenth Planet)

The Host of the Lupine Wavelength Haemovariform had all-black eyes. (TV: Tooth and Claw) Grace Holloway's eyes turned all-black when she was controlled by the Bruce Master. (TV: Doctor Who) 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)

Black roses grew on Florana. (AUDIO: The Elite)

Peter Dickson's mother thought that black cats were unlucky. (PROSE: The Clockwise Man)