I have never seen rusty rail on the side of track.
WOW! I don't know what to say? I would bet, you haven't been around here much?
Even if he hasn't been around the OGR Forums much, that still doesn't mean he is incorrect. Having been "around the real railroads" pretty much all my life, "rusty/red" rail is generally associated with unused or new rail. Rail that has been "in service" and heavily used, such as main line rail, tends to accumulate that brownish color in today's modern world of real railroading.
Back in the "old days" of steam and oil lubricated plain bearing equipped rilling stock, the sides of the rails tended to have a dark "greenish" coating, due to all the journal oil (which was indeed green color) which dripped out of everything.
I must admit that some folks that spray, or brush, paint the sides of their train tracks red, sure makes them look toy-like in my opinion.