For any given locomotive, go to the specification sheets, on line, from SMU, link included above. Specification sheets include boiler jacket material, boiler band material, cylinder wrappers, cab material and finish and some painting information.
Go to the Pacificng Baldwin page, [
www.pacificng.com] follow the links about painting styles as defined in the Stanford University's Baldwin paint books.... (for example Lake & Gold, style 1, aka Eureka)
The striping/painting system was not adopted until mid 1874 so the earliest locomotives lack the same information. Instead they call out "Best Passenger" or similar descriptions. In that case you have to look at photos of similar locomotives built at the same time. SMU holds three paint memo books, which include some information for pre-style system locomotives.
The finish code, also known as the Brass Foundry list helps with trim.
With all of this we still have not found hard information about cab roof color, running board color or how the top of the tender was finished... Not from lack of trying. The above works for Baldwin only... We have less on other builders
Randy