Cobalt 17

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The Azure Plains of the planet Cobalt 17 were a predominantly blue location.

After giving someone the task of drawing an arbitrary alien landscape around a picture of the Doctor's TARDIS, and then colouring it to match, the Thirteenth Doctor cited "park[ing] [the TARDIS] on the Azure Plains of the planet Cobalt 17" as being against the rules of the game, as the point was for the Doctor to get to see her box in a different coat of paint than the usual TARDIS blue. (GAME: Colour Chameleon)