Lustrous Spar Sky

From the Latin lustrare, to illuminate — used as a color word since the seventeenth century for hues with the slight specular shine of polished metal or silk. Lustrous green, lustrous gold: the implication is moderate-to-high saturation combined with surface reflectivity. Sits at the bright-and-glossy corner alongside gleaming.

Old Norse sparri, long-pole. As a color modifier, spar implies a long-wooden-pole-for-sail quality, the visual register of Tall-Ship-and-Royal-Navy-spar hand-cut long-wooden-pole-and-spar-for-sail mast-and-yard-and-boom maritime-rigging surfaces under tall-ship-spar-and-yard maritime-rigging light. Sits at the modifier-and-nautical end of the grid, parallel to mast and boom 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.