The club has a page of paint codes that mostly uses the NCS 1950 system (Can we put a link from the restoration section please).
I found that if you use the following website and select NCS 1950 and enter a paint code such as Atco S5040G30Y into the drop-down as S 5040-G30Y it will list alternative paint codes. (From the menu Advanced / Colour Alternatives).
Since tinned enamel paint suppliers often use BS381C codes, then Atco comes out as BS381C 221 Brilliant Green. I am not sure if this is for the new or older darker Atco colour though (I expect its for the new).
I also found that there is a NCS 1950 Digital Atlas for all the NCS colours, e.g.
The -G30Y colours are on page 40. Some longer copies of this Atlas found online also give all the CMYK codes at the end, so you can also look for equivalents based on the CMYK values, which don't always agree with the above.
After all this I came up with this list, but there still seems to be plenty of room for variation. So what colours have you used? This is for those of us who may not want to get an exact match, but just want to order the nearest BS standard tin ...
C M Y K
Cylinder Red S1085Y85R Not listed in the Atlas!
Ransomes S4030G30Y 50 0 70 45 BS381C 218 Grass green
Qualcast S4040G30Y 68 0 90 40 BS381C 218 Grass green (yes it comes out the same)
Atco S5040G30Y 60 0 90 60 BS381C 221 Brilliant green
Shanks S6030G30Y 50 0 80 72 BS381C 225 Light Brunswick green
Which paints have you used? Paragon, Tekaloid, Tractol, Agriline or Central Spares (which are currently not listing any)?
I was looking for the old Ransomes paint colour (1906) and for a Greens garden roller.