Heartening Phosphor
Heartening Phosphor (#66631B) is a deep yellow with a warm character. It leans warm, pulling light toward red, orange, and yellow. Naturally inviting, it suits editorial and hospitality contexts. Its HSL profile (58°, 58%, 25%) places it in the balanced band at a dark lightness. It works well as a headline, icon, or deep background in an otherwise light layout, pairing cleanly with cream, bone, and warm neutrals. For a confident two-color system, pair it with its complementary blue. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Old English heorte (heart) — present-participle of hearten. As a color modifier, heartening implies a clear-and-uplifting-and-encouraging quality where the hue carries the visual register of cheerful-encouraging color-tone. Sits at the crisp-and-cheerful end of the grid, parallel to welcoming and cheerful in usage.
A chemical that emits light when excited by an external energy source — the green-and-yellow phosphors of cathode-ray tubes, the yellow phosphor coatings of fluorescent tubes, and the white-LED yellow phosphor over a blue LED. The color refers to a yellow-phosphor-coated LED at full brightness: a saturated, slightly cool yellow with the optical brightness of electroluminescent emission.
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.