Blueprint
Open in tool →Cyan and indigo on navy is the developer-tool look; amber is the only warm note, so it always reads as 'attention'.
Color
#181529
#181529
hex
#181529rgb
rgb(24, 21, 41)hsl
hsl(249, 32%, 12%)oklch
oklch(0.21 0.039 289.5)Closest name: Dark Knight (#151931)Relative luminance 0.0089
Colors that go with #181529
Charcoal, Dark Olive Green and Sea Green 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.
Charcoal #36454f
neutralshippedCharcoal is the text near-black for #181529: softer than #000 and cool enough to feel like part of the same palette.
Dark Olive Green #556b2f
complementaryshippedDark Olive Green sits directly opposite #181529 on the wheel — the strongest contrast one hue can give another, so use it small: a button, a link colour, one highlight.
Sea Green #2e8b57
split-complementshippedSea Green is a split-complement of #181529: nearly opposite, so it still pops against it, without the vibrating edge of a true complement.
Sienna #a0522d
split-complementshippedSienna is a split-complement of #181529: nearly opposite, so it still pops against it, without the vibrating edge of a true complement.
Slate Blue #6a5acd
analogousshippedSlate Blue is #181529's neighbour on the wheel, so the two read as one family — use it for hover states, gradients and secondary surfaces.
Steel Blue #4682b4
analogousshippedSteel Blue is #181529's neighbour on the wheel, so the two read as one family — use it for hover states, gradients and secondary surfaces.
Teal #008080
triadicshippedTeal completes a triad with #181529 — three hues spaced evenly round the wheel, the classic way to get energy into a palette without a clash.
Amber #ffbf00
shippedAmber is paired with #181529 in 18 real palettes, including Blueprint and Southwest Airlines's brand system, as the accent.
Real palettes that use #181529
Tints & shades
Harmonies
Contrast
| #181529 as text | Ratio | AA | AA large | AAA | Fix |
|---|---|---|---|---|---|
Aaon white | 17.82:1 | pass | pass | pass | Passes AAA — no fix needed. |
Aaon black | 1.18:1 | 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 #181529 as the background.
Brands using this color
Palettes built around it
Indigo SaaS
Open in tool →The dependable indigo-and-emerald B2B pairing: indigo for primary actions, emerald reserved for success states.
Slate Workspace
Open in tool →Slate on slate with a single blue — the productivity-app look where the interface disappears behind the work.
Clinic
Open in tool →Teal reads clinical without the coldness of pure blue; the coral accent adds warmth for reassurance moments.
Cobalt Pop
Open in tool →One deep cobalt and one hot pink on white — a two-accent system for launches and campaign pages that need punch.
Dusk Gradient
Open in tool →Orange and peach on indigo-black with a violet — the last five minutes of a sunset, as a dark mode.
Sapphire & Gold
Open in tool →Deep sapphire and gold with a teal — old-money jewel tones on an ivory ground; heraldic without a crest.
Fonts for this mood
#181529 reads as cool, muted, dark. The font library is tagged with the same vocabulary:
mcpConnect your agent — build around #181529
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 #181529 and generate a 5-color palette that keeps it as the primary; give me the /palettes/new link
tool url
/palettes/new/181529-a79cc4-dfae4e-271f2d-e9ecf1?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