Color

#b21301

#b21301
hex#b21301
rgbrgb(178, 19, 1)
hslhsl(6, 99%, 35%)
oklchoklch(0.486 0.191 30.6)
Closest name: All Systems Red (#b30103)Relative luminance 0.0993

Colors that go with #b21301

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 →

#01a0b2

#b20148 · #b26b01

#01b213 · #1301b2

Split-complementary

Open in tool →

#01b26b · #0148b2

#48b201 · #01a0b2 · #6b01b2

Contrast

#b21301 as textRatioAAAA largeAAAFix
Aaon white
7.03:1passpasspassPasses AAA — no fix needed.
Aaon black
2.99:1failfailfail
  • AA: use #e91801 as the text (4.6:1)
  • AAA: use #fe6452 as the text (7.16:1)
  • AA: or shift the background to #cfcfcf (4.51:1)
  • AAA: or shift the background to #ffffff (7.03:1)

Fixes keep hue and saturation and move lightness only, so the suggestion stays on-brand. Ratios are symmetric: the same numbers apply with #b21301 as the background.

Brands using this color

Fonts for this mood

#b21301 reads as warm, vivid, playful. The font library is tagged with the same vocabulary:

mcpConnect your agent — build around #b21301
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 #b21301 and generate a 5-color palette that keeps it as the primary; give me the /palettes/new link

tool url/palettes/new/b21301-c4a59c-62cba3-2d271f-f1e9ec?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