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. (COMIC: Dreadnaught)

Rose Tyler wore a bomber jacket of indigo leather. (TV: Partners in Crime, Turn Left, The Stolen Earth, Journey's End)

Donna Noble wore an indigo blouse. (TV: Planet of the Ood)