Mourning
As noted by the Sixth Doctor, mourning was represented by the colour blue on "a number of civilised worlds" including Necros, but notably not Earth. As such, he wore a blue coat as a mourning suit. (TV: Revelation of the Daleks, WC: Real Time/AUDIO: Real Time)
The Tenth (TV: The Age of Steel) and Twelfth Doctors felt that mourning ought to wait until the danger was over. (TV: Mummy on the Orient Express) The Tenth Doctor urged everyone, for the time being, to "move on" from the death of Ricky Smith whilst London was still under attack by Cybermen. (TV: The Age of Steel) The Twelfth Doctor refused Perkins a moment to mourn the loss, seconds before, of Hector Quell, saying:
No, no, no. We can't do that. We can't mourn. People with guns to their heads, they cannot mourn. We do not have time to mourn.
After Adric's death, the Fifth Doctor, Nyssa and Tegan agreed that they would miss him, but the Doctor insisted that he "wouldn't want [them] to mourn unnecessarily". The Doctor opted instead to attempt to take his companions on a trip to the Great Exhibition of 1851, in order to "cheer [them] all up" and take their minds off the grief which they shared. (TV: Time-Flight)
