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)

Rose Tyler wore an indigo leather jacket before, during, and after the Planetary Relocation Incident involving the New Dalek Empire and Davros. (TV: Partners in Crime, Turn Left, The Stolen Earth|Journey's End)

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)

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

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)