Green

Green was the official colour of mourning in Perfugium, as it symbolised death and a return to nature. (AUDIO: Master) and the universal colour for medicine. (COMIC: A Confusion of Angels)

It sat between blue and yellow on the visible spectrum. (TV: Sky)

Verdant/forest green were two names for a certain shade of green. (PROSE: Enter Wildthyme)

Amy Pond wore a scoop collar top done in green (TV: The Lodger)

Bill Potts wore an emerald green velvet overcoat when visiting the 1814 frost fair (TV: Thin Ice)

Toshiko Sato wore a green blouse (TV: Out of Time).

Doctor Olivia Steele wore a pale green blouse underneath a white lab coat. (PROSE: Exodus Code)

The Master's eighteenth incarnation wore a dark green shirt up to his death, (TV: World and Enough|The Doctor Falls)

Time Lords of the Arcalian Chapter wore green ceremonial robes. (TV: The Deadly Assassin)

Sontarans had green blood. (TV: The Two Doctors, The Last Sontaran; AUDIO: The Heroes of Sontar)

Skaro's life including Kaleds own green blood (AUDIO: The Juggernauts)

Many species had green skin, including Alpha Centaurans, (TV: The Curse of Peladon) Etydions, Foamasi, Ice Warriors, (TV: Cold War) Jadeans, Jagaroth, (TV: City of Death) Kleptons, Primitives, Rutans, (GAME: The Gunpowder Plot) Silurians, (TV: The Hungry Earth) Swampies, (TV: The Power of Kroll) Urbankans, (TV: Four to Doomsday) Vinvocci (TV: The End of Time) and Watermen. (COMIC: Dr. Who Meets the Watermen) The Abzorbaloff (TV: Love & Monsters), infant Chimerons (TV: Delta and the Bannermen) and larval Wirrn (TV: The Ark in Space) were also green.

Nardole noted that, while he had been blue at one point, he had never been green. (COMIC: A Confusion of Angels)

Stahlman's ooze was green. (TV: Inferno) The waste from Global Chemicals' oil-refining process was green. (TV: The Green Death) The sky of an Earth-like planet was green, (PROSE: The Sour Note) as was the sky of Arcopolis. (PROSE: The Eyeless)

During the Middle Ages, green was associated with witches and was considered unlucky. (PROSE: Wolfsbane)

Green Daleks were at the Gallifreyan warship Starbane. (GAME: The Doctor and the Dalek)

In Through the Eye of Eternity, the Green Eye of Eternity generally symbolised that the week's episode would concern ecological themes. (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)

Behind the scenes
In the comic adaptation of the film Dr. Who and the Daleks, the police box-shaped TARDIS is erroneously coloured green as opposed to TARDIS blue.