Honda only lists the base colour, in the case of Rothmans, white - NH196. The other colours (blue, red, gold etc.) were depicted with stickers, so there are no "official" colour codes, as far as I know, but... if I were brave enough, I'd take a guess that the fuel tank is based on an "R" model. That would make the blue PB231 "Real Blue".
Best bet, like Wayne says, is to take a panel (if you have an original) or a sticker (get a small Rothmans sticker from a Honda dealer) to a good auto-body repair/paint shop, and have them match it against their colour charts.
Of course, the other colours aren't necessarily standard either. The red on the race-bikes was almost fluorescent for example. For a true replica, you will need to match all the colours at the paint shop.
If you have the bodywork sprayed in the base coat NH196 Ross White, you can order the genuine sticker kit from Honda. Get the body-shop to apply the stickers and you can't go wrong! The sticker part numbers can be found in the Online Parts Manual.
If you are fitting aftermarket bodywork, such as TYGA's GP fairing, I'd recommend you simply buy each of the smallest coloured stickers from Honda. That way you will have a match for every colour, and the spray-shop can paint the stripes for you! The sickers on the top fairing, would probably be the smallest/cheapest, looking at the diagrams.
Andy.
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