Useful Hour Teal

Latin ūsus, use — adjectival suffix -ful. As a color modifier, useful implies a clear-and-purpose-serving quality where the hue carries the visual register of helpful-and-supporting design-element. Sits at the crisp-and-functional end of the grid, parallel to practical and serviceable in usage.

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.

Anas crecca, the small dabbling duck whose male in breeding plumage sports a chestnut head crossed by a glossy green-blue stripe. The color refers to that stripe — the iridescent panel just behind the eye: a saturated, slightly muted blue-green with the optical depth of structural color rather than pigment. Cooler than cypress, warmer than cerulean, with the ornithological specificity of a color named for one feather of one bird.