Technically you can do both.
A copyright is when you've fixed an expressed idea into a fixed medium.
So the words you typed here for example, are automatically protected by copyright.
So I can 't collect the "best of Railroad.Net" and publish a book on my own.
So, a paint scheme, much like a building is protected by copyright.
HOWEVER, as you note, copyrights expire, trademarks don't.
Trademarks protect an expression in a particular field. The classic (though complicated) is Apple Records had a copyright on Apple when it came to music, and Apple Computers when it came to computers. But I could still have created "Apple Pie Company" that used an Apple as a logo.
So in the case of a paint scheme, I'm not sure the relevant case law.
My best guess is, if it's protected by copyright, you couldn't say, paint your car in a McGinnis paint scheme because you'd violate their copyright AND trademark.
Once it's out of copyright protection then they MIGHT be able to get you on trademark infringement, but among other things, they have to prove that a reasonable person might be confused into thinking you had their endorsement or something. Which, they'd probably win.
Briefly looking, my guess is the McGinnis paint scheme was probably protected under the 1908 Copyright act, which basically gave 56 years from the time it was filed. So you can use that.
For trademark I'd have to look, but my guess is it's still protected. So anyone, especially a RAILROAD trying to use it, had better make sure they have a legal right to do so.
And given that I've seen Metro-North locos (E7s I believe) painted in it recently, I'm guessing MNRR somehow owns or has obtained the rights.
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