You may recall a few silly expositions about paint colours on models a few years ago, and more recently, I've been agonizing over colors so that I can buy some paint and thus make some progress on a 9mm DG I've been working on for about a decade now.
Agonizing, because as Dave Turner would say, you can make colour look "accurate" and you can make it look "good", but those two are not always the same thing - sometimes our perception is skewed by a bunch of factors that were discussed in that aforementioned post.
An embarrassing example of this in my models (and in my photoshopping) that I've suspected for a while but have recently proved: I've tended to make my fruit salad and kiwirail international oranges too 'red'. It's my preference, but I have an inkling its not right – and I should be getting as close to "accurate" as possible and tweaking subtly from there.
Kevin Crossado for years has kindly put the British Standard (BSC) paint codes in model railway journal articles, but unfortunately those don't mean much to most people - even if you go to most professional places to go to get paints mixed up they don't want to hear about them. What you need is to be able to convert those BSC codes into something they understand.
So here's a useful website that has the BSC colors – for example international orange is…: http://www.e-paint.co.uk/Lab_values.asp?cRange=BS%20381C&cRef=BS381%20592&cDescription=International%20orange
This conveniently gives us some more useful conversion tools that let me to match an RAL colour that Resene Auto and Industrial have in their multi-volume book of paint swatches. Of course I thought this looked too "orange" and not "red" enough, so I borrowed the swatch book and ran it down to the Timaru yards in the hope of finding a KiwiRail DSG. Soon enough a pair of DFTs came through on a train and ...I was proved wrong. Despite their grunginess, KiwiRail Persimmon is Fruit Salad International Orange - and both are far orangier than I expected.
Super useful on that weblink are the RGB (red/green/blue) values familiar to many users of imaging and design software.
From this, here's an even more useful site for modelers: http://scalemodeldb.com/paint which lets us enter RGB values (international orange is 206/79/55) to give us the closest match in model paints!!! You can filter by brand to just pick Humbrol or Vallejo or whatever you prefer; and presto.