Sniper Grey is pretty light, much lighter than Sig Dark Grey.
There is a Stone Grey but I think it has some metallic in it. I actually think Sig Dark Grey has a microscopic amount of metallic in it too, but you have to get in certain light at certain angles to see it.
Cobalt is pretty much a black metallic. Cool color but I don't think it's what you are going for.
If you are wanting to stay away from that, my recommendation would be to start with Combat Grey and add armor black to it. Maybe start at 80:20 and increase the black from there to get to where you are headed.