Open Bog Sky

Old English open, unobstructed — used as a color modifier since the eighteenth century for hues that read as airy or uncrowded. Open blue, open green: moderate saturation combined with optical spaciousness, the slight visual breath of a hue that doesn't crowd the surface it covers. Sits at the crisp-bucket center alongside clear.

Irish bog, soft-and-wet. As a color modifier, bog implies a peat-soaked-and-soft quality, the visual register of Connemara-and-Yorkshire-Moors peat-bog blanket-bog-and-cotton-grass wet-and-sphagnum-moss surfaces under wet West-of-Ireland atmospheric overcast. Sits at the modifier-and-place end of the grid, parallel to fen and moor 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.