Ted makes an interesting point, and it brings up something that periodically bugs me about 0 gauge trains - how do you tell what is or is not authentic in a paint job? The Lionel PS-1's are an excellent example. I have several of them, but I couldn't tell you which of them are prototypical. Now, give me a freight car marked Milwaukee Road and I can usually tell if it's real, or I can look it up in my extensive Milwaukee Road library. But I can't tell you what is or is not real for most of the other railroads, and to have a library where you could look up that information for all the Class 1 railroads would be inconceivably expensive and take up an impossible amount of space. I don't mind the occasional fantasy color scheme - but I'd sure like to know what I'm getting.
Atlas is, to the best of my knowledge, the only 0 gauge train builder that verifies all of its paint jobs to be correct. They will paint anything on custom runs, but their own issues are at least claimed to be 100% prototypical. I know they are diligent about that, because I worked with them on the Milwaukee Road version of the extended vision caboose and it is the only fully correct Milwaukee EV caboose, although Lionel, MTH, and K-Line have all made the same caboose with varying degrees of authenticity.
I wish Lionel, MTH, etc. would include a little note with each car about the prototypical authenticity of the item - e.g. fully prototypical, prototypical for a different car (say, a paint job on a 40' single door car that in the real world was applied only to a 50' double door), complete fantasy, etc. But I don't think that's going to happen any time soon.