Untroubled Beam Sky

Latin turbāre, to disturb — negative-prefix un- plus past-participle of trouble. As a color modifier, untroubled implies a clear-and-calm-and-undisturbed quality where the hue carries no visual agitation. Sits at the crisp-and-calm end of the grid, parallel to serene and placid in usage.

Old English bēam, tree-or-ray-of-light. As a color modifier, beam implies a focused-and-shaft-of-light quality, the visual register of lighthouse-and-cathedral-clerestory-beam hand-focused-and-shaft-of-light lighthouse-and-cathedral-clerestory-and-search-light beamed-and-focused-and-shaft-of-light surfaces under lighthouse-and-cathedral-clerestory-and-search-light coastal-headland-and-Gothic-nave-and-night-sky directed-light. Sits at the modifier-and-mood end of the grid, parallel to ray and gleam 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.