Color

#b31209

#b31209
hex#b31209
rgbrgb(179, 18, 9)
hslhsl(3, 90%, 37%)
oklchoklch(0.488 0.192 29.5)
Closest name: All Systems Red (#b30103)Relative luminance 0.1004

Colors that go with #b31209

Royal Blue, Steel Blue and Teal lead the list. Each partner is a real named colour with the reason it works — a wheel relationship, a neutral that carries it, or a pairing lifted from a palette or brand system that actually shipped — and every pair opens in the palette tool.

Tints & shades

Every swatch is its own page — click any to analyze it.

Harmonies

Complementary

Open in tool →

#09abb3

#b30956 · #b36709

#09b312 · #1209b3

Split-complementary

Open in tool →

#09b367 · #0956b3

#56b309 · #09abb3 · #6709b3

Contrast

#b31209 as textRatioAAAA largeAAAFix
Aaon white
6.98:1passpassfail
  • AAA: use #ae1109 as the text (7.28:1)
Aaon black
3.01:1failpassfail
  • AA: use #e9170c as the text (4.59:1)
  • AAA: use #f7675f as the text (7.06:1)
  • AA: or shift the background to #d1d1d1 (4.57:1)

Fixes keep hue and saturation and move lightness only, so the suggestion stays on-brand. Ratios are symmetric: the same numbers apply with #b31209 as the background.

Brands using this color

Palettes built around it

Fonts for this mood

#b31209 reads as warm, vivid, playful. The font library is tagged with the same vocabulary:

mcpConnect your agent — build around #b31209
live endpoint

Point any MCP client at the shared colors endpoint and your agent gets the same engine as this page — direct_palette, edit_direction, check_palette, check_contrast — read-only, no key. Every direction it proposes comes with a /colors/d/… link: open it, lock what you like, paste the link back, and the agent edits rather than re-rolls.

endpointhttps://mcp.brandsweets.com/colors/mcp
claude mcp add --transport http brandsweets-colors https://mcp.brandsweets.com/colors/mcp
try this prompt

analyze #b31209 and generate a 5-color palette that keeps it as the primary; give me the /palettes/new link

tool url/palettes/new/b31209-c4a39c-62cb9d-2d261f-f1e9ed?lock=0&style=vibrant

Want the agent to remember your picks and write them into a living brand? Create a free BrandSweets workspace.

Machine-readable: color.md