Effective Tǔ
Effective Tǔ (#AC915F) is a true amber 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 (39°, 32%, 52%) places it in the balanced band at a mid lightness. It works across type, buttons, and borders, saturated enough to feel deliberate but balanced enough to not fight the rest of the palette. For a confident two-color system, pair it with its complementary azure. For something softer, pull in its analogous neighbors on either side of the wheel.
Etymology
Latin effectīvus, productive — adjectival suffix -ive. As a color modifier, effective implies a clear-and-purpose-achieving quality where the hue carries the visual register of successful-task-completion design-element. Sits at the crisp-and-functional end of the grid, parallel to practical and useful in usage.
The Chinese word for earth — the warm yellow-tan of loess soils that defined the cradle of Chinese civilization in the Yellow River valley. Tǔhuáng (earth-yellow) refers specifically to the loess deposits visible in the soil profile of Shaanxi and Gansu. The color refers to fresh loess in late-autumn light: a soft, slightly muted warm yellow-tan with the matte finish of fine wind-blown sediment.
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.
This color sits well within the sRGB cube. P3 and sRGB share the gray axis and most desaturated tones, so a P3 display renders this identically to an sRGB display.