On that very brochure, near the end, it says
"Range of colors available. Consult your Norton Dealer".
Your Norton dealer had a separate page showing colors. A 1971 page showing patches of colors available was on ebay a while back, so they do exist. Anyone got one for 1973 ??
That brochure also doesn't show all the colors available, other different brochure pages show more colors, including that lighter metallic 850 blue like the bike for sale.
Even Kims Commando CD doesn't have the color pages, are they that elusive ??
Cheers.