“Since earth is earth, perhaps, not heaven (as yet) / It only gives our wish for blue a whet,” writes Robert Frost in his 1920 poem Fragmentary Blue, in which he laments the fact that the divine color appears on the ground merely from time to time, becoming an ever-elusive link tying us to the firmament above. In winter, more than any other time of year, the azure hue reigns supreme, and the earth, if just for a moment, mirrors the sky.