Brown
From Tardis Wiki, the free Doctor Who reference
Mocha was a dark shade of brown named after a certain drink.
The War Doctor wore a double-breasted trenchcoat of mocha leather with peaked lapels when he and Skole faced Valmoria during the Last Great Time War. (AUDIO: In Name Only)
River Song wore a mocha fedora when solving a mystery in Vienna and 107 Baker Street during the 1920s, (AUDIO: Whodunnit?) and during an adventure on New York during 1938. TV: The Angels Take Manhattan)
