From Roberts helpful thread.

I've just been killing some time looking through this thread:. Station Colours Info site   and most interesting it was. Having said that, I suppose it'll cost me a fortune in paints now, oh well.  :)

Nice site Peter ! I've popped it in as a link  :thumbs

Lots of potential in this for (unfortunately) painting as we know it today (or as various preservation societies do it), rather than what was found 100+ years ago. Paint in the early days was ground (with varying pigment lots) and mixed on site using linseed oil as the carrier (excellent for wood and for metal, where it acted as an antioxidant), and was subject to a lot more oxidation (from sunshine and smoke) than would be commonly found with modern paints. Aging turns linseed oil yellow. Add to that variations as local painters made their own adjustments to head office instructions. Freshly painted versus 10-15 years of weathering. Chocolate brown. Hmm. Milk or dark? GWR cream. White (original) or yellow (oxidized)? Bottom line is that those old paint formulations got very yellow with age. Lots of scope for variations in color by adding black and or yellow to commercial offerings.

Nigel