Useful Blink Sky

Latin ūsus, use — adjectival suffix -ful. As a color modifier, useful implies a clear-and-purpose-serving quality where the hue carries the visual register of helpful-and-supporting design-element. Sits at the crisp-and-functional end of the grid, parallel to practical and serviceable in usage.

Middle Dutch blinken, to-shine-or-twinkle. As a color modifier, blink implies a quick-and-twinkling-and-on-off quality, the visual register of lighthouse-beam-and-firefly-blink hand-quick-and-twinkling-and-on-off lighthouse-beam-and-firefly-and-Morse-lamp blinked-and-quick-and-twinkling surfaces under lighthouse-beam-and-firefly-and-Morse-lamp coastal-headland-and-summer-meadow rotating-and-pulsed-light. Sits at the modifier-and-mood end of the grid, parallel to wink and glint 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.