Harbour
Open in tool →Steel blue and haze with a buoy orange on a pale grey — the maritime palette every port town uses for a reason.
Color
#3f557d
#3f557d
hex
#3f557drgb
rgb(63, 85, 125)hsl
hsl(219, 33%, 37%)oklch
oklch(0.45 0.071 261.8)Closest name: Deep Indigo (#4c567a)Relative luminance 0.0903
Colors that go with #3f557d
Sea Green, Sienna 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.
Sea Green #2e8b57
triadicshippedSea Green completes a triad with #3f557d — three hues spaced evenly round the wheel, the classic way to get energy into a palette without a clash.
Sienna #a0522d
complementaryshippedSienna sits directly opposite #3f557d on the wheel — the strongest contrast one hue can give another, so use it small: a button, a link colour, one highlight.
Blue #0000ff
shipped4 real palettes, including CVS's brand system and Alaska Airlines's brand system put Blue beside #3f557d, as the supporting colour.
Cornflower Blue #6495ed
shippedDesigners have shipped Cornflower Blue with #3f557d: 4 real palettes, including Coca-Cola's brand system and Blizzard's brand system, as the supporting colour.
Crimson #dc143c
shippedCrimson is paired with #3f557d in 10 real palettes, including Amazon's brand system and Codecademy's brand system, as the supporting colour.
Denim #1560bd
shippedDesigners have shipped Denim with #3f557d: 12 real palettes, including HP's brand system and Dutch Bros's brand system, as the accent.
Firebrick #b22222
shippedDesigners have shipped Firebrick with #3f557d: 4 real palettes, including Fireside and Campbell's's brand system, as the lead colour.
White Smoke #f5f5f5
neutralWhite Smoke is the surface for #3f557d: a clean near-white with no warm cast, so the cool hue stays clear instead of drifting muddy.
Real palettes that use #3f557d
Tints & shades
Harmonies
Contrast
| #3f557d as text | Ratio | AA | AA large | AAA | Fix |
|---|---|---|---|---|---|
Aaon white | 7.48:1 | pass | pass | pass | Passes AAA — no fix needed. |
Aaon black | 2.81:1 | fail | fail | fail |
Fixes keep hue and saturation and move lightness only, so the suggestion stays on-brand. Ratios are symmetric: the same numbers apply with #3f557d as the background.
Brands using this color
No public brand in the corpus uses this exact color yet. Extract a brand to add one.
Palettes built around it
mcpConnect your agent — build around #3f557d
live endpointPoint 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.
endpoint
https://mcp.brandsweets.com/colors/mcpclaude mcp add --transport http brandsweets-colors https://mcp.brandsweets.com/colors/mcp
try this prompt
›analyze #3f557d and generate a 5-color palette that keeps it as the primary; give me the /palettes/new link
tool url
/palettes/new/3f557d-9ca5c4-df664e-211f2d-e9f0f1?lock=0&style=vibrantWant the agent to remember your picks and write them into a living brand? Create a free BrandSweets workspace.
Machine-readable: color.md