Purple

Periwinkle was a light shade of blue and purple.

The Thirteenth Doctor wore a hooded, periwinkle trenchcoat with midnight blue interim, apart from the sleeves, which had lavender insides, and a rainbow pattern along the edges. (TV: The Woman Who Fell to Earth-The Power of the Doctor) The Spy Master briefly wore her trenchcoat when he processed her body as part of his master plan. (TV: The Power of the Doctor)

The Sixth Doctor wore a periwinkle cravat when he and Grant Markham foiled Nomad Cybermen on Agora during 2191. (PROSE: Killing Ground)

Sarah Jane Smith wore a periwinkle skirt suit when she met the K1 Robot. (TV: Robot)

Rose Tyler wore a periwinkle hoodie when she met Elton Pope and the Abzorbaloff. (TV: Love and Monsters)

Donna Noble wore a periwinkle tank-top when she and the Tenth Doctor met River Song and some Vashta Nerada. (TV: Silence in the Library/Forest of the Dead)