My books have conflicting information on this point, unfortunately.
However, I have a book with some photos of actual uniforms. The summer 1914 uniform, consisting of the M1907/10 tunic and trousers is in what is called "field grey." The tunic has a slight bluey tint to its grey hue, while the field grey of the trousers is more like a plain grey.
Another photo shows the M1914 tunic, which came slightly later, and was a simplified version of the above. It is still described as "field grey" but by this time that colour has morphed into something that has a green shade to it. The trousers are "stone grey."
The former has fancy cuffs, the latter plain cuffs. So I guess it depends what your figures are wearing.