Grey
From Tardis Wiki, the free Doctor Who reference
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 [+]Loading...["Four Doctors (comic story)"])
The Eleventh Doctor wore an ash scarf with his Victorian outfit. (TV: The Great Detective [+]Loading...["The Great Detective (TV story)"], The Snowmen [+]Loading...["The Snowmen (TV story)"])