Ballast
First off, HAPPY CANADA DAY!
Ballast color seems to change depending on the area that you are modeling. I grew up in California and modeled the desert where gray was the prevelent color, however brownish-red was used on some mainlines. Now I live in BC and notice some different colors. For one, there is coal being shipped to the docks and much spilled coal is on the ballast.
I know its a lot to thing about, but it is important to know that the color of ballast tells a lot about the area being modeled and about what was shipped on the mainline. Is iron ore shipped along your lines? That might be colorful.
Most important is to enjoy what you are doing.
-Ed Acosta