Effulgent Tarn
Effulgent Tarn (#40E4F3) is a true cyan with a neon character. It sits at the high-saturation edge of its family. Use it sparingly, as signage, accent, or highlight against darker surfaces. Its HSL profile (185°, 88%, 60%) places it in the highly saturated band at a mid 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 red. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Latin effulgēns, shining-out — present-participle of effulgere, sharing root with fulgor (lightning). As a color modifier, effulgent implies a saturated-and-radiating-light-out quality, the bright color of Renaissance-Madonna halo-and-aureole gold-leaf-and-pigment emission. Sits at the bright-and-saturated end of the grid, parallel to resplendent and radiant in usage.
A small mountain lake — particularly the cwm (cirque) lakes of the British Lake District, the Welsh hills, and the Norwegian peaks. From the Old Norse tjörn. Tarn color refers to a fresh-water tarn at Stickle Tarn in Cumbria: a saturated, slightly cool deep blue with the optical depth of cold-water mountain pool.
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.