A classic Doctor Who serial has been updated for a new era. Prior to 1978, the BBC did not concern itself with maintaining archives of its shows, which meant that many First (William Hartnell) and Second Doctor (Patrick Troughton) episodes were missing. Others, still, have poor audio quality and dated special effects. The surviving episodes from these early seasons are also all black-and-white, which can make it difficult to perceive the nuances of the actors’ performances. The BBC previously colorized the 75-minute First Doctor serial, “The Daleks”, but no other episodes have received that treatment.

https://screenrant.com/doctor-who-the-war-games-color-remaster-second-doctor-regeneration-new-footage/