Color
#663b91
#663b91rgb(102, 59, 145)hsl(270, 42%, 40%)oklch(0.446 0.139 304.4)Colors that go with #663b91
Charcoal, Crimson and Denim 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 #663b91: softer than #000 and cool enough to feel like part of the same palette.
Crimson #dc143c
shippedCrimson is paired with #663b91 in 4 real palettes, including Wells Fargo's brand system and Lenovo's brand system, as the lead colour.
Denim #1560bd
shippedDesigners have shipped Denim with #663b91: 6 real palettes, including Slack's brand system and Hinge's brand system, as the lead colour.
Midnight Blue #191970
shipped6 real palettes, including Kraken's brand system and First Snow put Midnight Blue beside #663b91, as the lead colour.
Royal Blue #4169e1
shippedRoyal Blue is paired with #663b91 in 4 real palettes, including Wayfair's brand system and Fivetran blue's brand system, as the supporting colour.
Tomato #ff6347
shipped6 real palettes, including FedEx's brand system and GitLab's brand system put Tomato beside #663b91, as the supporting colour.
Dark Olive Green #556b2f
complementaryDark Olive Green sits directly opposite #663b91 on the wheel — the strongest contrast one hue can give another, so use it small: a button, a link colour, one highlight.
Blue #0000ff
shipped3 real palettes, including Zillow's brand system and CVS's brand system put Blue beside #663b91, as the lead colour.
Real palettes that use #663b91
Tints & shades
Harmonies
Contrast
| #663b91 as text | Ratio | AA | AA large | AAA | Fix |
|---|---|---|---|---|---|
Aaon white | 8.08:1 | pass | pass | pass | Passes AAA — no fix needed. |
Aaon black | 2.6:1 | 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 #663b91 as the background.
Brands using this color
Fonts for this mood
#663b91 reads as cool, modern. The font library is tagged with the same vocabulary:
Point 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.
https://mcp.brandsweets.com/colors/mcpclaude mcp add --transport http brandsweets-colors https://mcp.brandsweets.com/colors/mcp
›analyze #663b91 and generate a 5-color palette that keeps it as the primary; give me the /palettes/new link
/palettes/new/663b91-b59cc4-c9cb62-2c1f2d-eae9f1?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