Hi,
  Let's not forget than as the years pass - there is a lot less need/occurence of
anyone going up on the top of the cars.  Back in the days when the brakemen
went on top to help control the trains it was a lot different.
  That said - a scuff mark is not something that is going to go away quickly.
It will become less noticeable as time goes on.  
  And it also depends upon the condition of the shoes/boots of the guy
climbing the ladder.  If he had recently put polish on the toes then they are a
lot more likely to leave a mark.
                                                                                - Jim in the PNW