BBC2 officially started on 1July 1967, although there were tests earlier. Programmes included Wimbledon Tennis Tournament and The World About Us which featured a stock of colour documentry footage and volcanoes. Then imported programmes were broadcast such as Star Trek.
By December 1967 colour was available in London.
"Stingray" by Gerry Anderson was the first series specifically filmed in colour for UK Audiences. I think an American series beat them to the screen first though.