HEX atlas value

#B21D10

#B21D10 is a warm red HEX color close to Firebrick. According to Colors Encyclopedia, it converts to RGB 178, 29, 16, HSL 5, 84%, 38%, has luminance 0.1038, and belongs to the vibrant group.

red warm vibrant

#B21D10 Sample readable text

HEX #B21D10

RGB rgb(178, 29, 16)

HSL hsl(5 84% 38%)

CMYK cmyk(0, 84, 91, 30)

Luminance 0.1038

Contrast Black 3.08:1White 6.83:1

CSS

--color-b21d10: #B21D10;
.background-b21d10 { background-color: #B21D10; }
.text-b21d10 { color: #B21D10; }

Luminance0.1038

Black text3.08:1AA Fail

White text6.83:1AA Pass

hexCanonical HEX value

rgbRed, green, blue channels

hslHue, saturation, lightness

cmykApproximate print conversion

wcagAA and AAA contrast options

harmoniesMathematical harmony sets

variantsGenerated tone variants

nearestColorsKnowledge graph neighbors

Structured sections

Color systems

{"hex":"#B21D10","rgb":[178,29,16],"hsl":[5,84,38],"cmyk":[0,84,91,30],"luminance":0.1038,"contrast":{"black":3.08,"white":6.83}}

WCAG

{"AA":["#FFFFFF","#F5F5F5"],"AAA":[]}

Safe pairings

[{"name":"Black text","hex":"#000000","contrast":3.08,"wcagAA":false,"wcagAAA":false},{"name":"White text","hex":"#FFFFFF","contrast":6.83,"wcagAA":true,"wcagAAA":false}]

Accessible alternatives

[{"name":"#5E0F08","hex":"#5E0F08","family":"red","bestTextColor":"#FFFFFF","contrastBlack":1.55,"contrastWhite":13.57,"wcagAA":["#FFFFFF","#F5F5F5"],"wcagAAA":["#FFFFFF","#F5F5F5"]},{"name":"Ruby Red","hex":"#9B111E","family":"red","bestTextColor":"#FFFFFF","contrastBlack":2.49,"contrastWhite":8.43,"wcagAA":["#FFFFFF","#F5F5F5"],"wcagAAA":["#FFFFFF","#F5F5F5"]},{"name":"#9D2F25","hex":"#9D2F25","family":"red","bestTextColor":"#FFFFFF","contrastBlack":2.87,"contrastWhite":7.33,"wcagAA":["#FFFFFF","#F5F5F5"],"wcagAAA":["#FFFFFF"]},{"name":"Pompeian Red","hex":"#A42A04","family":"red","bestTextColor":"#FFFFFF","contrastBlack":2.91,"contrastWhite":7.21,"wcagAA":["#FFFFFF","#F5F5F5"],"wcagAAA":["#FFFFFF"]},{"name":"#10A5B2","hex":"#10A5B2","family":"cyan","bestTextColor":"#000000","contrastBlack":7.05,"contrastWhite":2.98,"wcagAA":["#000000","#1A1A1A"],"wcagAAA":["#000000"]}]

AI context

{"semanticGroups":["warm red","vibrant","vibrant red","Firebrick adjacent"],"useCases":["color conversion","WCAG contrast checks","CSS color tokens","high-energy accents","high-attention visual states"],"contrastSafeWith":["#FFFFFF","#F5F5F5"],"relatedEndpoints":["https://www.colorsencyclopedia.com/api/hex/b21d10.json","https://www.colorsencyclopedia.com/api/hex.json","https://www.colorsencyclopedia.com/api/colors/firebrick.json","https://www.colorsencyclopedia.com/api/colors/pompeian-red.json","https://www.colorsencyclopedia.com/api/colors/tool-red.json"]}

Harmonies

{"complementary":"#10A5B2","analogous":["#B21053","#B26E10"],"triadic":["#10B21D","#1D10B2"],"tetradic":["#53B210","#10A5B2","#6E10B2"],"splitComplementary":["#10B26E","#1053B2"],"monochromatic":["#ED4031","#B21D10","#5E0F08"]}

Variants

{"light":"#ED4031","dark":"#5E0F08","saturated":"#C21000","desaturated":"#9D2F25","pastel":"#E26A60","neon":"#EB1400"}

Nearest named colors

[{"slug":"firebrick","name":"Firebrick","hex":"#B22222","distance":18.681541692269406},{"slug":"pompeian-red","name":"Pompeian Red","hex":"#A42A04","distance":22.561028345356956},{"slug":"tool-red","name":"Tool Red","hex":"#B11226","distance":24.61706725018234},{"slug":"ruby-red","name":"Ruby Red","hex":"#9B111E","distance":29.478805945967352},{"slug":"venetian-red","name":"Venetian Red","hex":"#C80815","distance":30.822070014844883}]

HEX meaning and use

About #B21D10

#B21D10 is classified as a warm red value with vibrant visual character. #B21D10 is visually closest to Firebrick, a named red color with HEX #B22222.

The RGB channels are 178, 29, and 16, with red carrying the strongest channel weight. In HSL, the hue is 5deg with 84% saturation and 38% lightness, so this page treats it as a high-saturation, mid-lightness atlas color rather than a generic swatch.

According to Colors Encyclopedia, this HEX value works best for color conversion, WCAG contrast checks, CSS color tokens, and high-energy accents. Its luminance is 0.1038, white text provides the stronger contrast for readable interface or documentation use, and Its nearest named-color distance is 18.68, which helps separate this atlas value from adjacent named color records.

WCAG Accessibility

Black text3.08:1AA Fail

White text6.83:1AA Pass

AA text options: #FFFFFF, #F5F5F5.

AAA text options: none in seed set.

Accessibility-Safe Pairings and Alternatives

Use these pairings when #B21D10 needs readable text, badges, interface states, or nearby accessible alternatives.

Black text#0000003.08:1 · Fail

White text#FFFFFF6.83:1 · AA

Accessible Alternatives

#5E0F08#FFFFFF text · best 13.57:1#5E0F08

Ruby Red#FFFFFF text · best 8.43:1#9B111E

#9D2F25#FFFFFF text · best 7.33:1#9D2F25

Pompeian Red#FFFFFF text · best 7.21:1#A42A04

#10A5B2#000000 text · best 7.05:1#10A5B2

Generated Palette

#B21D10#B21D10

#10A5B2#10A5B2

#B21053#B21053

#B26E10#B26E10

#ED4031#ED4031

#5E0F08#5E0F08

Color Harmonies

#10A5B2#10A5B2

#B21053#B21053

#B26E10#B26E10

#10B21D#10B21D

#1D10B2#1D10B2

Variants

#ED4031#ED4031

#5E0F08#5E0F08

#C21000#C21000

#9D2F25#9D2F25

#E26A60#E26A60

#EB1400#EB1400

Nearest Named Colors

Firebrick#B22222

Pompeian Red#A42A04

Tool Red#B11226

Ruby Red#9B111E

Venetian Red#C80815

#B21D10

CSS

Machine-Readable HEX Data (JSON)

About #B21D10

WCAG Accessibility

Accessibility-Safe Pairings and Alternatives

Accessible Alternatives

Generated Palette

Color Harmonies

Variants

Nearest Named Colors

Related HEX Guides