Useful Dux 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 dux, leader-or-general. As a color modifier, dux implies a Latin-leader-and-Roman-general-and-Doge quality, the visual register of Roman-dux-and-Venetian-Doge hand-Latin-leader-and-Roman-general-and-Doge Roman-dux-and-Venetian-Doge-and-Renaissance-condottiere dux-and-Latin-leader surfaces under Roman-dux-and-Venetian-Doge-and-Renaissance-condottiere Republican-Rome-and-Venetian-Doge's-Palace leader-and-general-light. Sits at the modifier-and-Latin end of the grid, parallel to pater and virtus 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.