Untroubled Mater 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.

Latin mater, mother. As a color modifier, mater implies a Latin-mother-and-Stabat-Mater-and-Madonna quality, the visual register of Stabat-Mater-and-Pietà-mater hand-Latin-mother-and-Stabat-Mater-and-Madonna Stabat-Mater-and-Pietà-mater-and-Marian-iconography mater-and-Latin-mother surfaces under Stabat-Mater-and-Pietà-mater-and-Marian-iconography Roman-and-Counter-Reformation Madonna-iconographic-light. Sits at the modifier-and-Latin end of the grid, parallel to pater and amor 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.