I was led to believe that providing the paint code was all you needed. http://lotus-europa.com/colors.html
The paint shop I use is owned by ex Lotus employees.
They sprayed an Elan yellow, but when the yellow arrived, ordered to paint code, it was too orange (a bit like the Lotus badge)
so they sent it back. They then sprayed the Elan in a lighter yellow which looked really good.
I made sure they used the same yellow when they painted 4259R, my #5. It looks really good.
When I can get my Land Cruiser to start, I can pick it up and take in 4483R to be painted in JPS livery.
My other toy is sky blue and marigold. Replacement front and rear clams from the factory were a paler blue than the original, so even the factory can have a variation in colour.