The book " The History of Britain's Training Aircraft" by Ray Sturtivant contains a photo of 6 FTS Harvards in April 1950. The one nearest the camera is FS753 coded FB [ roundel ] GG. It's a black and white photo but this particular aircraft appears to be overall yellow with the usual black anti- dazzle surface in front of the cockpit.
Other Harvards in the photo are in the silver finish with yellow bands - can't see the serials but one is coded FB - HI.
Roundels and finflashes are all red, white and blue.
I've seen other pictures of 6 FTS Harvards but, at present, can't track them down - if I do, I'll post the details.