Certain Gemini Forest
Certain Gemini Forest (#138E30) is a deep green with a jewel character. It carries the deep, saturated richness of a gemstone. Authoritative and slightly formal, it works well for type and heavy UI elements. Its HSL profile (134°, 76%, 32%) places it in the highly saturated band at a dark lightness. Best used in small doses, like logos, CTAs, focus rings, or highlight text, where its saturation becomes a feature rather than noise. For a confident two-color system, pair it with its complementary magenta. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Latin certus, fixed / sure — sharing root with English concern and certify. As a color modifier, certain implies a saturated-and-unambiguous quality where the hue declares its character without hesitation. Sits at the bold-and-confident end of the grid, parallel to assured and decisive in usage.
Latin gemini, twins-of-the-zodiac. As a color modifier, gemini implies a twins-and-air-sign-and-Mercury-ruled-mutable-air quality, the visual register of Castor-and-Pollux-Gemini-twins hand-twins-and-air-sign-and-Mercury-ruled-mutable-air Castor-and-Pollux-Gemini-twins-and-Argonaut-twins gemini-and-twins-and-air-sign surfaces under Castor-and-Pollux-Gemini-twins-and-Argonaut-twins late-spring-and-May-and-June mutable-air-sign-light. Sits at the modifier-and-zodiac end of the grid, parallel to castor and pollux 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.
Closest matches
The nearest named color in three reference sources, ranked by perceptual distance (ΔE76 in CIELAB). ΔE < 1 is imperceptible to most viewers; ΔE > 10 is clearly different. When two sources point to the same hex they’re merged into one tile; click any to open that color’s page.
Variations
Click any swatch to exploreHarmonies
Accessibility
How this color appears to viewers with the four major color-vision-deficiency types. Computed via the Machado (2009) physiologically-based model. If a tile matches the original, the color reads the same to that viewer.
The color used as foreground text against pure white and pure black, with the contrast ratio and WCAG 2.1 grade. Aim for AA (4.5:1) for body text and AA Large (3:1) for 18 pt+ headlines; AAA (7:1) is the gold standard for long-form reading surfaces.
Wide gamut
The CSS Color 4 wide-gamut form of this color. Both swatches render the same color on every display — the P3 form only diverges from sRGB when a designer pushes channels outside sRGB's reach.
Moderately saturated colors gain a small bump in P3 — the difference is usually visible side-by-side on wide-gamut hardware but won't change the character of the color.