Indigo (colour)

You may be looking for the plant or the Caxtarid named Indigo.

Indigo was a colour between violet and blue on the visible spectrum. (TV: Sky)

The Eighth Doctor wore an indigo cravat when he first met Stacy Townsend during an encounter with Cybermen on the Dreadnought (COMIC: Dreadnaught)

The Fourth Doctor wore an indigo brocade waistcoat with a fob watch when he met Magnus Greel in London during 1892. (TV: The Talons of Weng-Chiang)

Rose Tyler wore an indigo bomber jacket before, during, and after the Planetary Relocation Incident involving the New Dalek Empire and Davros; and also during the Tenth Doctor's siphoned regeneration. (TV: Partners in Crime, Turn Left, The Stolen Earth|Journey's End) She also wore it when helping many versions of the Doctor and companions. (GAME: Lost in Time)

Martha Jones wore an indigo jumper with a v-neck collar, (TV: Smith and Jones, The Sontaran Stratagem; AUDIO: Dissected) as did her clone during the 2009 Sontaran Invasion of Earth. (TV: The Sontaran Stratagem|The Poison Sky)

Amy Pond wore an indigo tank-top under her scarlet v-neck and her chocolate brown leather jacket. (TV: Victory of the Daleks; GAME: City of the Daleks, Blood of the Cybermen, TARDIS, Shadows of the Vashta Nerada) She also wore an indigo t-shirt under her navy blazer. (TV: Amy's Choice)

The Dalek Time Strategist's casing was indigo. (AUDIO: The Shadow Vortex-The Enigma Dimension)

Clara Oswald wore an indigo mini-dress with African symbols done in gold during the 3W Institute Affair. (TV: Dark Water/Death in Heaven)

Josie Day wore an indigo cravat with her steel blue tailcoat and her lavender blouse. (COMIC: The Lost Dimension)

The Ninth Doctor wore an indigo jumper with a v-neck collar when helping the last of the Zetacene. (AUDIO: Last of the Zetacene)

Jorjie Turner wore an indigo t-shirt when she met Taphony. (TV: Taphony and the Time Loop)

Donna Noble wore an indigo blouse with daisy symbols during a dinner party. (TV: The Giggle)

The Monk wore a blazer of indigo houndstooth tweed. (AUDIO: The Rise of the New Humans)

Vortisaurs had indigo skin with stripes. (AUDIO: The Book of Kells)