Definition of "greyness"

The sight of them [the Grampians] as we crossed the viaduct over the North Esk I am not likely to forget. After a night of snow, they hung wraith-like across the sky, exquisitely beautiful in the greyness of winter dawn.

1947 January and February, O. S. Nock, “"The Aberdonian" in Wartime”, in Railway Magazine, page 8