Color

#3731dd

#3731dd
hex#3731dd
rgbrgb(55, 49, 221)
hslhsl(242, 72%, 53%)
oklchoklch(0.46 0.246 272.5)
Closest name: Lapis on Neptune (#1f22d2)Relative luminance 0.0823

Colors that go with #3731dd

Charcoal, Sea Green and Amber 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 →

#d8dd31

#3181dd · #8d31dd

#dd3731 · #31dd37

Split-complementary

Open in tool →

#dd8d31 · #81dd31

#dd3181 · #d8dd31 · #31dd8d

Contrast

#3731dd as textRatioAAAA largeAAAFix
Aaon white
7.94:1passpasspassPasses AAA — no fix needed.
Aaon black
2.65:1failfailfail
  • AA: use #6a65e6 as the text (4.62:1)
  • AAA: use #908dec as the text (7.21:1)
  • AA: or shift the background to #c4c4c4 (4.55:1)
  • AAA: or shift the background to #f2f2f2 (7.09:1)

Fixes keep hue and saturation and move lightness only, so the suggestion stays on-brand. Ratios are symmetric: the same numbers apply with #3731dd as the background.

Brands using this color

No public brand in the corpus uses this exact color yet. Extract a brand to add one.

Fonts for this mood

#3731dd reads as cool, vivid, technical. The font library is tagged with the same vocabulary:

mcpConnect your agent — build around #3731dd
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 #3731dd and generate a 5-color palette that keeps it as the primary; give me the /palettes/new link

tool url/palettes/new/3731dd-a29cc4-df9e4e-261f2d-e9edf1?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