I'll admit I do like running my passenger trains with the lights off.
I put LEDs in one of my aluminum OK Engines coaches and with the lights out they give off a bluish tint, I think mainly because the seats are a blue color and the light is bouncing off them onto the aluminum interior. I have a car with gray seats I need to try them in to see if it makes a difference.
I have LED headlights in all my steam and I'm surprised at how bright they are.