I have been a member of an American group, for a lot of years!, having an interest in the Colorado Midland which closed after WW1. But we had on going discussions about colour from every aspect. My conclusion is we will all see the same colour slightly differently so my stock will be the right colour and yours well, the jury's out!
In Back Track vol34 No2 For feb 2020 there is an article Irish Diesel traction by David Moseley worth having for the 6 colour photos. All green and yet more shades in the melting pot!