Sky blue
From Tardis Wiki, the free Doctor Who reference
Sky blue was the colour of a shirt the Eleventh Doctor wore throughout the latter half of his life, (TV: The Bells of Saint John, The Day of the Doctor, et alt.) leading up to his death and regeneration into the Twelfth Doctor (who consequently spent his first moments in that same shirt). (TV: The Time of the Doctor)
Diane Holmes also wore a sky blue shirt, with her sleeves rolled up, when adapting to the 21st century. (TV: Out of Time)
