A crayon was a writing utensil.
A young First Doctor drew crayon sketches of the Solvers, based on stories he was told on Gallifrey. The Eighth Doctor, upon meeting the genuine article, remarked that his drawings did not do her justice. (AUDIO: The Doomsday Chronometer)
Peter Summerfield drew all over Hass's notes with a green crayon. Bernice Summerfield gave him something less important on which to draw — something of Jason Kane's. (PROSE: Final Draft)
George Mann drew a sketch of Iris Wildthyme, Panda and Elspeth May using crayons and felt tip markers. (PROSE: Iris at the V&A)