There was only a small batch of silver Mustang IIIs, indeed most of them known from PAF but perhaps only because we have the best photo coverage.
Bulk (ie. all) of Mk IIIs were camouflaged, with standard markings but spinners. At early March 1945 coloured spinners were introduced to Polish Mustangs, 316 had white-red stripes. Cannot say about RAF Sqns, but apparently they have had coloured ones as well.