Purple

Periwinkle be a light shade between purple and blue.

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)