Well, Rochie....been studying the couple of photo's and doin' some reading...while watching Liverpool V Newcastle....
While I don't claim to be an expert on 'reading' B&W photo's Red 7 appears to have a low contrast scheme of probably 81/82 or 81/83 especially on the fuselage, a high contrast scheme of 75/83 would be rather obvious....much like the rudder shows, which just may be a replacement unit in these colours?
The port wing looks to be a lower contrast, bit washed out by the sunlight, than the visible portion of the starboard wing....it is possible that the wings could be 75/83...the aircraft for the most part were made in sub assemblies and were painted as such, then brought together for assembly.
there is one aircraft in the JaPo book that certainly fits this hypothesis.
...and red 7's style of camo probably puts this K-4 in the 331XXX W.Nr. block made in Nov-Dec 1944.