Mike,
Color is a hot button topic amongst OGR forumites.
Unfortunately you're currently asking for more than our system can deliver. Here's why, with apologies for the lengthy explanation:
In my opinion the two biggest questions we see on OGR online are:
1.) What color is it supposed to be?
2.) Why don't the colors match?
I'll try to tackle your question, but be prepared to see significant constructive criticism from other forumites to be applied to my analysis:
a.) Historical Sources for Color Standards -- Many of the liveries seen in our models come from the distant past. As such there is little to no good documentation on the precise colors used in those liveries. Most photos from back in the day are in black and white, and so help very little when trying to determine color accuracy.
b.) Means for Capturing Color Standards -- In at least some situations situations in the past railroads relied on color chips, or mixing recipes, as a record of the precise colors used on their equipment. However through many mergers, acquisitions, divestures, and shutdowns over the years these chips and recipes are very hard or impossible to find today. In some cases surviving railroads have been diligent in keeping track of their colors, using the chips or other means, in others not so much. Several historical societies have inherited color chips, formulas, descriptions, or color photos from defunct railroads and are good sources for color information, but there aren't many.
c.) Additional Efforts to Capture Accurate Color Standards -- At least one book publisher has made a strong effort to save color information captured in color photos. Almost all of these are post WWII, as color film technology became lest costly, and 99.9% of them are slides (Kodochrome). As these age the colors fade, so this publisher has tried to capture copies in books, because printed color on paper is thought to be more stable than color on film.
d.) Manufacturing History -- In the early years of toy trains and model railroading there were few manufacturers. Through the golden age of modeling (late pre-war through post-war era) most of these made large numbers of a small range of items, and thus had very tight control over the color consistency of their products, even over many years.
e.) No Central Repository -- On the other hand, because of (1) through (3) above, there has never been a "central repository of color information" for them to consult when mixing up their colors. Therefore good color consistency within a manufacturer's product line was common, even over many years, but between manufacturers was not too common at all during this period.
f.) Leadership -- In the transition from late post-war to the early modern era Lionel's products, because it was seen as the market leader and it's production was consistent, were often used by other manufacturers as samples to which they could match their colors. Consistency between manufacturers improved but was still not perfect.
g.) Shifting Manufacturing, Patterns -- Nowadays (Modern Era to present) there are many manufacturers, and all of them do much smaller production runs for their items. This is largely because consumers are increasingly interested in more esoteric railroads and liveries, are more picky about details, and are presented with several levels of historical accuracy in scale and those details. More product lines, involving lower production volume in each, are now the norm.
h.) Shifting Manufacturing, Geography -- Added to that production of product has shifted from local and easily accessible to far, far away with significant communications roadblocks frequently in the way. Just like a coffee taster, or a sommelier for wine, there used to be a single expert with each company that was responsible for getting it right, at least for their company. This works well when that expert can visit the production facility often in order to make sure that colors are consistent. It doesn't work well when factories are thousands of miles away. All forms of quality control are much harder over longer distances.
i.) Applying Technology -- On the other hand it's not impossible. Color matching technology has and has emerged, and improved significantly, in the last 30 years. However it's apparently too expensive for the manufacturers that supply our hobby. Contrast this with your ability to go into a home center and have the paint department mix up a custom color from any item you can physically carry into its store.
Fixing this mess is doable. It will take effort and money, but doesn't everything that's worthwhile?
Good luck with your color matching efforts.
M.H.M.