Hi Rosa and Maurice, do you mean WW1 or WW2? for WW1 I use Foundry stone grey for Infantry jackets and trousers. I haven't tried Foundry Granite, but i imagine it might also be quite pleaseing.
For WW2 i used Storm Green for the jackets, and Stone grey for the trousers for the infantry, and Storm green all over for the gebirgsjager.
To be honest, i tend to use whatever looks 'nice' rather than what is completely accurate, although as far as i understand, there are so many different shades of Field Grey that you can't go too far wrong.