i would start with metallic gray, wash with black and dark rust. if the tracks are used chrome silver on the top og the rail, if not leave it black washed. at /72 i usually build my own. i have a miter saw for cutting basswood to ties length. unfortunately, germans did not spike theit track like americans did so, in order scratchbuild you have to make a billion rail to tie clips.
for the plastic ties i would paint dark brown and wash with dark grays. ballast could be medium or light gray depending on how much contrats you want.
just some thoughts.
scrratchbuild rails at 1/72
