Would 00 track be near enough in scale? Then paint as rust and scrape off the top surface.With traffic running over them wouldn't the tops of the rails be shiny steel?
The sleepers would have a wide degree of colour variation, depending on how each has absorbed creosote/tar. Also there'd lines of grease and accumulated dust on the sleepers and ballast.
Really depends on how much detail you want to put on what is a secondary feature.