Untroubled Libra 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 libra, scales-of-the-zodiac. As a color modifier, libra implies a scales-and-air-sign-and-Venus-ruled-cardinal-air quality, the visual register of Roman-Libra-and-scales-of-justice hand-scales-and-air-sign-and-Venus-ruled-cardinal-air Roman-Libra-and-scales-of-justice-and-Themis-Astraea libra-and-scales-and-air-sign surfaces under Roman-Libra-and-scales-of-justice-and-Themis-Astraea autumn-equinox-and-September-and-October cardinal-air-sign-light. Sits at the modifier-and-zodiac end of the grid, parallel to virgo and scorpio 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.