Plain Seth Sky

Latin planus, flat, level — used as a color modifier since the medieval period for hues that read as undecorated and direct. Plain white, plain blue: moderate saturation, no shift, no surface effect. Sits in the crisp-bucket center, with the implication of restraint rather than absence.

Egyptian Set, god-of-storms-and-desert-chaos. As a color modifier, seth implies a desert-storm-and-chaos-god quality, the visual register of Egyptian-Seth-and-Ombos-temple hand-desert-storm-and-chaos-god Egyptian-Seth-and-Ombos-temple-and-Osirian-conflict seth-and-desert-storm-and-chaos-god surfaces under Egyptian-Seth-and-Ombos-temple-and-Osirian-conflict Western-Desert-and-storm-cloud red-desert-storm-light. Sits at the modifier-and-myth end of the grid, parallel to horus and ptah 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.