Ink & Paper
Open in tool →Two greys and one ink-blue link color: the palette of a well-set book page.
Color
#243fb7
#243fb7
hex
#243fb7rgb
rgb(36, 63, 183)hsl
hsl(229, 67%, 43%)oklch
oklch(0.432 0.191 267.4)Closest name: Cobalt Blue (#0047ab)Relative luminance 0.0735
Colors that go with #243fb7
Medium Sea Green, Midnight Blue and Slate Gray 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.
Medium Sea Green #3cb371
shippedMedium Sea Green is paired with #243fb7 in 4 real palettes, including Fintech Trust and Indigo SaaS, as the accent — a combination designers have actually shipped, not a computed rotation.
Midnight Blue #191970
shippedMidnight Blue is paired with #243fb7 in 5 real palettes, including Blue Mono and Fintech Trust, as the text colour against it — a combination designers have actually shipped, not a computed rotation.
Slate Gray #708090
shippedSlate Gray is paired with #243fb7 in 4 real palettes, including Ink & Paper and Campus, as the supporting colour — a combination designers have actually shipped, not a computed rotation.
Olive Green #808000
complementaryOlive Green sits directly opposite #243fb7 on the wheel — the strongest contrast one hue can give another, so use it small: a button, a link colour, one highlight.
Charcoal #36454f
neutralshippedCharcoal is the text near-black for #243fb7: softer than #000 and cool enough to feel like part of the same palette.
Steel Blue #4682b4
analogousshippedSteel Blue is #243fb7's neighbour on the wheel, so the two read as one family — use it for hover states, gradients and secondary surfaces.
Sienna #a0522d
split-complementSienna is a split-complement of #243fb7: nearly opposite, so it still pops against it, without the vibrating edge of a true complement.
Powder Blue #b0e0e6
shippedPowder Blue is paired with #243fb7 in two real palettes: Glacier and First Snow, as the supporting colour — a combination designers have actually shipped, not a computed rotation.
Real palettes that use #243fb7
Tints & shades
Harmonies
Contrast
| #243fb7 as text | Ratio | AA | AA large | AAA | Fix |
|---|---|---|---|---|---|
Aaon white | 8.5:1 | pass | pass | pass | Passes AAA — no fix needed. |
Aaon black | 2.47:1 | 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 #243fb7 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
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.
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.
Fonts for this mood
#243fb7 reads as cool, vivid, technical. The font library is tagged with the same vocabulary:
mcpConnect your agent — build around #243fb7
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 #243fb7 and generate a 5-color palette that keeps it as the primary; give me the /palettes/new link
tool url
/palettes/new/243fb7-9c9fc4-df7e4e-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