Pellucid Lough Sky

Latin pellūcidus, transparent — derived from per-lūcēre (to shine through). As a color modifier, pellucid implies a clear-and-translucent quality where the hue reads with optical clarity and minimal turbidity. Sits at the crisp-and-clear end of the grid, parallel to lucid and translucent in usage.

Irish-and-Scottish loch via Old Irish loch, lake / sea-inlet. As a color modifier, lough implies a still-mountain-water quality, the visual register of Connemara-and-Lough-Erne Irish-Highland glacial-cirque-and-river-mouth still-and-mirror-smooth fresh-water surfaces under Western-Irish overcast light. Sits at the modifier-and-place end of the grid, parallel to mere and pond 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.