Defined Bell Sky

Latin dēfīnīre, to set bounds — past-participle of define. As a color modifier, defined implies a clear-and-edge-distinct-and-precise quality where the hue carries the visual register of sharp-bounded-and-clearly-delimited surface. Sits at the crisp-and-clear end of the grid, parallel to crisp and sharp in usage.

Old English belle, bell. As a color modifier, bell implies a hour-marked-and-tolling quality, the visual register of English-and-Russian-bell-tower hour-marking-and-tolling cathedral-bell-and-bell-tower clock-and-time-marking surfaces under hour-marked-bell tolling-bell-tower light. Sits at the modifier-and-time end of the grid, parallel to knell and hour 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.