Yes, RR299 was one of two T.III Mosquitos used in '633 Squadron' (1963), and 'Mosquito Squadron' (1968), the others being TT.35s slightly modified to resemble the FB.VI version. The T.IIIs appeared in background, taxiing, or 'long' shots, with the TT35s being the main type seen in close-up.
The fictional (for a Mosquito Sqn) codes were applied for the film (she'd previously been painted overall 'Aluminium'), and retained throughout the remainder of RR299's life, even after the airframe was recovered and re-painted, at Hawarden, around 1981. In 1994, she had 'D-Day' stripes applied, for the 50th anniversary of D-Day airshow season, which were removed the following year.
I've seen most 'stills' from both movies, which are mainly B&W shots, and this particular colour shot looks like one of a series taken much later, at a UK airshow.