I've got one! Original Fireflake Royal Blue, never painted. I was never able to find a matching set of unpainted sidepanels in good condtiion though. A couple of times I saw a single sidepanel on ebay (they bring good money), but never a matched set.
There were actually two shades of blue metalflake bodywork: Royal Blue like my tank, and Sapphire Blue on the earlier models. Royal Blue is a little darker and was produced for the 1970 through 1972 model years. Sapphire Blue was 1969 only (according to Roy Bacon).
Yes, there seems to be a lot of uncertainly on metallic blue color Commandos. My buddy who has a one owner '69 'S' swears that blue was not offered in '69. The blue and red tanks on the '69 and '70 'S' had huge metalflake in them. Of course this was gelcoat and not paint. I bought a NOS 1971 Fireflake Royal Blue Fastback tail section from the NOC spares scheme in the early '80's that was much smaller flake. We would call it metallic as opposed to metalflake. You can see it even in the '71 brochure
http://www.classicbike.biz/Norton/Brochures/1970/1971Commando.pdf. Quite different from the '69-'70 stuff.
Then I bought my 750 Roadster in 1973, again it's called Fireflake blue, but is a steel tank and the color is paint. This is definitely a metallic and appears to be over a black or dark base. (Still has tthe orginal paint)
A friend bought a '74 850 Roadster in blue and it was obviously over a lighter base and had no dark flecks in it as my set does.
My point is all these were listed as Fireflake Royal blue in the parts books, but look quite different. I've never found a reference to the Sapphire Blue other than in Bacon's book.