Good stuff Geo.
I've just checked a couple of references and, although the official specification called for the 'Aluminium' finish on the MkIV, there were some finished in camouflage, as evidenced by Geo's pic, and the one posted below.
This shows a newly- delivered MkIV (P-51K) of 19 Sqn at Peterhead in April, 1945,with the Sqn CO and pilots, but look at the left background, and there's a camouflaged MkIV (P-51D) of the same squadron.
This has got my interest going, as the pilots I mentioned earlier had all flown the 'K' variant, all in 'silver' finish, and I'm wondering if the Dallas-built 'K' was delivered in 'silver', with the Inglewood 'D' either delivered in camouflage, or painted in the UK. Perhaps it was even to enhance the performance of the 'K', as all the pilots I've spoken too remarked that the'K' didn't have the 'Oomph' of the 'D', presumably due to the Aeroproducts prop, as has been mentioned numerous times in various accounts?
Certainly later, all variants seemed to be in the painted silver finish, and I'm sure Xtradecal must have had solid information on which to base their decal sheet, although there are a couple of serial numbers on the sheet which are definitely 'K' variants.
Incidentally, on all variants/colour schemes in the Squadron, the nose and spinner were white, with mid-blue bands, and later, blue checks were added to the white nose band, aft of the spinner.