Useful Sol 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 sol, sun-and-Roman-sun-god. As a color modifier, sol implies a Roman-sun-god-and-stellar-disc quality, the visual register of Roman-Sol-Invictus-and-Apollo-sun hand-Roman-sun-god-and-stellar-disc Roman-Sol-Invictus-and-Apollo-sun-and-Helios-chariot sol-and-Roman-sun-god-and-stellar-disc surfaces under Roman-Sol-Invictus-and-Apollo-sun-and-Helios-chariot December-25-and-Helios-and-quadriga noon-stellar-disc-light. Sits at the modifier-and-zodiac end of the grid, parallel to luna and terra 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.