No 233 (Harrier) OCU markings

No 233 OCU originally formed on 1/9/52 at RAF Pembrey, near Kidwelly, South Wales, and the unit’s badge depicted a black Welsh Wildcat, taken from the Kidwelly Town Coat of Arms. The OCU disbanded on 1/9/57.

No 233 (Harrier) OCU re-formed at RAF Wittering on 1/10/70, but it was not until late 1973 that OCU markings appeared on the side of the noses of their Harrier GR1/1As. These markings were a black Welsh Wildcat in a pale blue circle, with two coloured bars on either side, coloured red/blue & yellow/black. On 1/9/92, 233 OCU was renumbered No 20(R) Squadron, and the unit’s markings were a combination of the 20 Sqn markings, as worn by their former aircraft since 1961, and the former 233 OCU Harrier markings. The black Welsh Wildcat was positioned on the fin of their Harrier GR5s, and the coloured bar markings were positioned on the top of the fin of the aircraft.

I am trying to find out when in 1973, that the 233 OCU markings appeared on the aircraft, and also, what is the significance of the four coloured bar markings.