The OFFICIAL start of colour TV was indeed Dec 2nd 1967.
See:
https://en.wikipedia.org/wiki/1967_i...ish_television
There's a lot more out there to back that up.
I also recall a front of cover of 'Practical Television' saying 'Colour is Here - Starts Dec 2nd'.
The Wimbledon broadcasts were still experimental - even though they were claimed to be 'regular'. The BBC was playing a game of 'first' with Germany, France and the USSR over colour TV in Europe, but in the end - as is usual with 'firsts' - it boils down to definitions of that 'first'. The official date for the start of colour TV in the UK is Dec 2nd 1967 (on BBC2 only), but you can play with the definitions all day!
Best regards,
Paul M