Pleasant Hour Sky

From the French plaisant, pleasing — used as a color modifier since the fifteenth century for hues that read as agreeable, the kind of color that wears well over a long viewing without becoming demanding or fatiguing. Pleasant green, pleasant rose: moderate saturation combined with optical comfort. Sits at the crisp-bucket alongside easy and calm.

Latin hōra, time-of-day. As a color modifier, hour implies a single-time-period quality, the visual register of Edwardian-and-Victorian household clock-marked single-hour-of-the-day domestic-and-formal interior surfaces under hour-by-hour pendulum-clock day-light. Sits at the modifier-and-time end of the grid, parallel to bell and vesper 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.