The instrument panel on all Spitfires was semi-matt, or matt Black, not 'blue-green'. I reckon the colour the instructions refer to is the British 'cockpit green', which is a pale green with a slight blue-grey tinge. This was used to paint the interiors of most British aircraft during the period of World War Two, and the remainder of the Spitfire's cockpit was painted this colour. There are various paints from differing manufacturers that are a close match, but I normally mix my own. If you have a look at the thread '30 Years of Airframes' Models', you'll find a shot of my Spit MkIX and Spit MkIa showing this colour. The pics of the MkIX are a closer match, as the lighting for the MkIa makes the colour look darker.
Hope this helps.
Terry.