It's regularly quoted that painting the side of track makes it look realistic. A look out the window on any train journey I've been on shows the track at best to be dark brown or more usually black. Some products on the market for this purpose are a brown-red colour, but I think brown or black is more similar to my observations...
... these photos show code 80 track with waterbased (poster) paint applied to the rails with a brush...
Above: This shot shows the near side track painted with brown paint, and the far track painted with black paint.
Above: The nearside track is brown paint as before, but the far track is black mixed with brown paint.
Above: Again, this shot shows the near side track painted with brown paint, and the far track painted with black paint but this time on brown/grey ballast.
I've yet to experiment with aerosol paints for the colouring / weathering.
I think that either the brown or the black is a slight improvement on the unpainted appearance.
The use of grey ballast appears too "clean" so the track painting stands out too much. I think the grey ballast would have to be weathered in some way to reduce the effect of the dark rails standing out.
On the final picture, the use of brown-grey ballast makes a rail colour of brown or grey work.