Blue Mono
Open in tool →One blue at four lightnesses — monochromatic in the colour-theory sense; the deep step is the text, the pale step the surface tint.
Color
#21274f
#21274f
hex
#21274frgb
rgb(33, 39, 79)hsl
hsl(232, 41%, 22%)oklch
oklch(0.29 0.073 274.5)Closest name: Black Market (#222244)Relative luminance 0.0234
Colors that go with #21274f
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 #21274f: softer than #000 and cool enough to feel like part of the same palette.
Dark Olive Green #556b2f
complementaryshippedDark Olive Green sits directly opposite #21274f 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
triadicshippedSea Green completes a triad with #21274f — three hues spaced evenly round the wheel, the classic way to get energy into a palette without a clash.
Sienna #a0522d
split-complementshippedSienna is a split-complement of #21274f: nearly opposite, so it still pops against it, without the vibrating edge of a true complement.
Slate Blue #6a5acd
analogousshippedSlate Blue is #21274f'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 #21274f's neighbour on the wheel, so the two read as one family — use it for hover states, gradients and secondary surfaces.
Amber #ffbf00
shippedAmber is paired with #21274f in 8 real palettes, including Beach Hut and Southwest Airlines's brand system, as the supporting colour.
Blue #0000ff
shipped19 real palettes, including Sketch's brand system and Monzo's brand system put Blue beside #21274f, as the accent.
Real palettes that use #21274f
Tints & shades
Harmonies
Contrast
| #21274f as text | Ratio | AA | AA large | AAA | Fix |
|---|---|---|---|---|---|
Aaon white | 14.31:1 | pass | pass | pass | Passes AAA — no fix needed. |
Aaon black | 1.47:1 | 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 #21274f as the background.
Brands using this color
Palettes built around it
Fonts for this mood
#21274f reads as cool, dark, luxury. The font library is tagged with the same vocabulary:
mcpConnect your agent — build around #21274f
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 #21274f and generate a 5-color palette that keeps it as the primary; give me the /palettes/new link
tool url
/palettes/new/21274f-9c9dc4-df864e-231f2d-e9eef1?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