In a word, no

Modern main line rail is well maintained, so there's a fair chance that what you were looking at was fairly new rail.  It rarely sits around long enough to get the old red brown rusty color that the smaller secondary rails have.  However, it very definitely rusts, and it looks rusty.  When the rails have been in place for a year or two, the entire swath of main line, including rails, tie plates, ties, and ballast looks like it's been spray painted a light oxide brown for about 8" on either side of the rails.

I see

I see what you mean. After looking at some more photos of various lines, I see that some grey rails have the beginnings of rust showing and others are light brown.

I now have a better idea about what to paint my rails with, thanks.

Mike Ruby