One of the many benefits to having a snow-covered landscape is our optical ability to distinguish based on contrast. The delectable palette of winter is quite splendid when sorted by our sight. A full spectrum is on display, but one color seemingly prevails over all others. It is blue.
Spend enough time in the most frigid of seasons and you will see that it uses all of the blues there are. A shade is present for water, snow, and ice. The shadows of trees and mountains cast other variations. And, as they lay in various depths before us, each layer becomes lighter blue based on the furthering of distance. The skies, whether day or night, represent most other variations of blue. The chromaticity overhead ranges from azure to zaffre.
When I hear of others speak of the winter blues, my response is usually in accord. I am grateful they are able to see them, too.