Solid Keep Forest

Latin solidus, firm, dense — used as a color modifier since the seventeenth century for hues that read as continuous and unbroken: a solid blue is one with no variation across the surface. Implies high saturation combined with optical density. Sits in the bold-bucket alongside strong and robust, slightly more focused on uniformity.

Old Norse keypa, to-keep. As a color modifier, keep implies a fortified-castle-keep-and-strongtower quality, the visual register of Norman-and-Welsh-castle-keep hand-built fortified-castle-keep-and-stronghold-tower medieval-and-Norman-castle architectural surfaces under medieval-Norman-and-Welsh castle-keep-and-stronghold light. Sits at the modifier-and-architecture end of the grid, parallel to tower and crenel in usage.

The dense canopy of a temperate or tropical woodland — oak, beech, pine, eucalyptus, mahogany — wherever leaves close above to filter the light below. Forest green refers to the average reflectance of a healthy mid-summer canopy seen from below: a saturated, slightly muted green with the matte finish of layered chlorophyll. Deeper than fern, cooler than olive, with the ecological weight of a word that has named every wooded biome on Earth.