Color

#51b4e1

#51b4e1
hex#51b4e1
rgbrgb(81, 180, 225)
hslhsl(199, 71%, 60%)
oklchoklch(0.729 0.113 230.8)
Closest name: Blue Martini (#52b4d3)Relative luminance 0.3983

Colors that go with #51b4e1

Charcoal, Amber and Blue 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 →

#e17e51

#51e1c7 · #516be1

#e151b4 · #b4e151

Split-complementary

Open in tool →

#e1516b · #e1c751

#c751e1 · #e17e51 · #6be151

Contrast

#51b4e1 as textRatioAAAA largeAAAFix
Aaon white
2.34:1failfailfail
  • AA: use #1d7daa as the text (4.6:1)
  • AAA: use #155d7e as the text (7.24:1)
  • AA: or shift the background to #3d3d3d (4.64:1)
  • AAA: or shift the background to #1f1f1f (7.04:1)
Aaon black
8.97:1passpasspassPasses AAA — no fix needed.

Fixes keep hue and saturation and move lightness only, so the suggestion stays on-brand. Ratios are symmetric: the same numbers apply with #51b4e1 as the background.

Brands using this color

Fonts for this mood

#51b4e1 reads as cool, vivid, technical. The font library is tagged with the same vocabulary:

mcpConnect your agent — build around #51b4e1
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 #51b4e1 and generate a 5-color palette that keeps it as the primary; give me the /palettes/new link

tool url/palettes/new/51b4e1-9cb3c4-df4e66-1f232d-e9f1f0?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