This is actually the one part that is easy - Barre granite is fairly uniform in color and grain, that's part of what made it into the so-called "Granite Capital of the World". Color can vary a bit from quarry to quarry of course, but generally the unpolished stone looks a lot like this:
https://www.usgs.gov/media/images/barre-granite
Granite from other parts of Vermont is different. Woodbury/Hardwick granite is darker with a coarser grain, Bethel is typically much lighter, almost looking like marble.
I haven't been super happy with my
attempts to find a suitable paint color, but I'm getting there - effectively it's a very light gray from a distance. The challenge is that just flat gray doesn't look right, but I've been able to improve the look by adding multiple layers of different colored weathering chalk on top of the paint.