Ash was a shade of grey named after a certain substance.
The War Doctor wore ash leather gaiters when he helped Voord during the Last Great Time War. (COMIC: Four Doctors [+]Paul Cornell, Titan summer events (Titan Comics, 2015).)
The Eleventh Doctor wore an ash scarf with his Victorian outfit. (TV: The Great Detective [+]Steven Moffat, Doctor Who Children in Need Special 2012 (BBC One, 2012)., The Snowmen [+]Steven Moffat, Doctor Who Christmas Special 2012 (BBC One, 2012).)
Rose Tyler wore an ash grey hoodie during the 2006 Sycorax Invasion of Earth. (TV: The Christmas Invasion)
Sarah Jane Smith wore a burgundy and ash jumper with green diamonds when she and the Third Doctor helped to save Peladon from Azaxyr and Eckersley; (TV: The Monster of Peladon [+]Brian Hayles, Doctor Who season 11 (BBC1, 1974).) and when helping to deal with Rutans in England during the 1970s. (AUDIO: The Children of the Future)
Ruby Sunday wore an ash grey jumper with maroon stripes in a parallel timeline. (TV: 73 Yards)
Melody Pond wore an ash grey tank top with a raven black leather jacket as Mels Zucker. (TV: Let's Kill Hitler)