Healthful Moor Sky

Old English hǣlth, health — adjectival suffix -ful. As a color modifier, healthful implies a clear-and-vital-and-wholesome quality where the hue carries the visual register of fresh-air-and-sunlight outdoor health-promoting environment. Sits at the crisp-and-wholesome end of the grid, parallel to salubrious and wholesome in usage.

Old English mōr, waste / marshland. As a color modifier, moor implies a heather-covered-upland quality, the visual register of Yorkshire-and-Scottish-Moors heather-and-bracken-covered peat-bog-and-grouse-shooting upland surfaces under late-summer purple-heather Yorkshire-and-Highland atmospheric light. Sits at the modifier-and-place end of the grid, parallel to bog and wold in usage.

The blue of a clear sky at noon — produced by Rayleigh scattering, the preferential dispersion of shorter wavelengths through atmospheric molecules. Air itself is colorless; the color we see is sunlight scattered toward our eyes by every cubic kilometer above. The reference shade is mid-latitude noon under a high pressure system: a clean, slightly green-shifted blue with the luminous depth of light scattered across an entire hemisphere of air.