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Authoritative Slab Crimson

#a91c1b
Notes

Authoritative Slab Crimson (#A91C1B) is a true red 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 (0°, 72%, 38%) 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 cyan. For something softer, pull in its analogous neighbors on either side of the wheel.

HEX
#a91c1b
RGB
rgb(169, 28, 27)
HSL
hsl(0, 72%, 38%)
HWB
hwb(0 11% 34%)
OKLCH
oklch(47.5% 0.176 27.5)
P3
color(display-p3 0.6083 0.1695 0.1410)
HSV
hsv(0, 84%, 66%)
LAB
lab(36.64% 54.67 38.47)
LCH
lch(36.64% 66.85 35.13)
CMYK
cmyk(0%, 83%, 84%, 34%)

Etymology

Authoritative
adjective

Latin auctōritāt-, authority — adjectival suffix -ive. As a color modifier, authoritative implies a saturated-and-formal-imperative quality where the hue carries decisional weight and institutional credibility. Sits at the bold-and-authoritative end of the grid, parallel to commanding and magisterial in usage.

Slab
modifier

Old French esclape, splinter / slab. As a color modifier, slab implies a flat-thick-stone-or-wood quality, the visual register of Cotswold-and-Yorkshire-flagstone-and-slab hand-quarried-and-flat-thick stone-and-timber-and-marble hand-quarried-flat-thick-slab surfaces under Cotswold-and-Yorkshire flagstone-and-slab quarry-light. Sits at the modifier-and-texture end of the grid, parallel to plate and tile in usage.

Crimson
noun

From the Old Spanish cremesin, itself from the Arabic qirmiz — the kermes scale insect, dried and ground into a brilliant carmine dye prized in the medieval Mediterranean. For centuries the most expensive red on a draper's shelf, reserved for cardinals, kings, and the cloth that gave English the word crimson. Cooler than scarlet, deeper than rose; the color of pomegranate seeds and a serious occasion.

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 explore

Harmonies

Accessibility

Color-vision simulation

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.

#a91c1b
Original
#4b4319
Protanopia
#6d6113
Deuteranopia
#bb001e
Tritanopia
#3a3a3a
Achromatopsia
WCAG contrast

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.

The quick brown foxSample body text at normal size. The wcag minimum for body contrast is 4.5:1 (AA) or 7:1 (AAA).
AAAon White
7.32:1
The quick brown foxSample body text at normal size. The wcag minimum for body contrast is 4.5:1 (AA) or 7:1 (AAA).
Failon Black
2.87:1

Wide gamut

Display P3 representation

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.

sRGB hex
sRGB hex
##A91C1B
Display P3
Display P3
color(display-p3 0.6083 0.1695 0.1410)
P3 has subtle headroomOKLCH chroma 0.176

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.

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