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
#21234f
#21234f
hex
#21234frgb
rgb(33, 35, 79)hsl
hsl(237, 41%, 22%)oklch
oklch(0.281 0.079 278)Closest name: Azulado (#211d49)Relative luminance 0.0209
Colors that go with #21234f
Charcoal, Dark Olive Green and Sienna 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 #21234f: softer than #000 and cool enough to feel like part of the same palette.
Dark Olive Green #556b2f
complementaryshippedDark Olive Green sits directly opposite #21234f on the wheel — the strongest contrast one hue can give another, so use it small: a button, a link colour, one highlight.
Sienna #a0522d
split-complementshippedSienna is a split-complement of #21234f: nearly opposite, so it still pops against it, without the vibrating edge of a true complement.
Slate Blue #6a5acd
analogousshippedSlate Blue is #21234f'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 #21234f'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 #21234f — 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 #21234f in 9 real palettes, including Southwest Airlines's brand system and Beach Hut, as the accent.
Blue #0000ff
shipped18 real palettes, including Sketch's brand system and Monzo's brand system put Blue beside #21234f, as the accent.
Real palettes that use #21234f
Tints & shades
Harmonies
Contrast
| #21234f as text | Ratio | AA | AA large | AAA | Fix |
|---|---|---|---|---|---|
Aaon white | 14.81:1 | pass | pass | pass | Passes AAA — no fix needed. |
Aaon black | 1.42:1 | 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 #21234f 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
Fonts for this mood
#21234f reads as cool, dark, luxury. The font library is tagged with the same vocabulary:
mcpConnect your agent — build around #21234f
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 #21234f and generate a 5-color palette that keeps it as the primary; give me the /palettes/new link
tool url
/palettes/new/21234f-9f9cc4-df924e-251f2d-e9edf1?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