The one thing I always loved about model railroading was the ability to buy any engine and give it a new livery (colors and logos) to become the stars on my N and S Railroad without fear of a visiting expert chiding me about miniscule details that make up his rail world, not mine.
Manufacturers Agree
You will find a growing trend among model railroad equipment manufacturers to get beyond the confines of prototypical design.But it is your space, use it as you see fit.