I have read in several articles that Green Zinc Chromate is not really the correct color. Below is a part of the IPMS Stockholm article regarding the P-51 interior color as well as the anti-glare on the nose.
You can find the entire 3 part article here; http://www.ipmsstockholm.org/magazine/2004/02/stuff_eng_interior_colours_us_part2.htm
North American P-51 Mustang
In the beginning, the P-51 was built exclusively to the British specifications. In the Mustang Mk. I production, North American reportedly used colours that were substitutes of the official colours of the RAF.
When the P-51B came about, it was probably painted Dull Dark Green throughout the cockpit.
The June 1944 Structural Repair Manual for all version of the P-51 calls for overall Interior Green in the cockpit, in the area extending from the instrument panel to the back of the canopy. An exception from the rule was that areas not normally visible required no finish coat. Instrument panel was specified as Instrument Black.
According to the same source, pilot's seat and the anti-glare forward decking were to be painted Dull Dark Green. However, there are clues indicating that this colour may not have been used on any on the items. Based on the inspection of preserved aircraft, Dana Bell claims that at least some of the seats of the P-51 were painted Bronze Green rather than Dark Dull Green. Likewise, many wartime colour photographs consistently show Olive Drab in the anti-glare area.
Another subject of long-going controversy is the colour of the cockpit floor, which in P-51 was made of plywood. Erection and Maintenance instructions for the P-51D specify all wood floor areas to be covered in black non-skid surfacer purported to be a mix of silica sand and matt black paint, the kind of finish that was also used for wing walks. Metal floor areas were to be left in bare metal finish.
The December 1944 update of Erection & Maintenance Manual for the P-51D follows the same description with the exception of anti-glare decking inside the canopy which was to be painted black.
Similarly to other aircraft types, the camouflaged P-51 most probably had wheel wells painted in Neutral Grey. On later-production natural metal aircraft, the wheel wells were Interior Green. Additional piping and wiring inside the wheel well area was painted in Aluminium lacquer.
Hope this helps