Complementary color generator
Find the color directly across the wheel — and the schemes around it — in one click.
Open the palette generator →What complementary means
Complementary colors sit opposite each other on the color wheel, 180° apart. Paired well, they create strong, high-energy contrast — great for calls to action. GenHub's palette tool also offers analogous, triadic and tetradic harmonies if you want something softer or more varied.
Use it with contrast in mind
High contrast is striking but can be hard to read. The palette tool shows WCAG contrast ratios so you can check text legibility against each color before you commit.
Beyond complementary: the other harmonies
GenHub's palette tool includes six harmony modes: auto (a pleasant default mix), monochrome (one hue, varying lightness), analogous (neighboring hues, naturally cohesive), complementary (opposite hues, high contrast), triadic (three hues evenly spaced, vibrant but balanced) and tetradic (four hues in two complementary pairs, the most varied). Complementary is the highest-contrast option; if it feels too aggressive, analogous or monochrome give a calmer result from the same base color.
Where complementary works best
- A single call-to-action button against a calmer background palette.
- Sports or event branding that wants energy and visibility.
- Data visualization where two categories need to read as clearly opposed.
It works less well for large body-text areas, where that much contrast becomes fatiguing to read.
Checking it's actually usable
A striking color pair can still fail as a text-and-background combination. Run any complementary pairing through the built-in WCAG contrast checker before shipping it — it reports the exact ratio and whether it clears AA (4.5:1 for normal text) or AAA (7:1) against both white and black.
A short history of the color wheel
The idea of "opposite" colors goes back to 18th- and 19th-century color theory — the notion that certain hue pairs, viewed side by side, appear to intensify each other. That basic principle still holds in a modern sRGB or HSL wheel, even though the exact wheel layout has been refined many times since. It's why a complementary pair is such a reliable first move for anything that needs to grab attention: a sale badge, a warning state, a single standout data point in a chart.
Generating one for your brand
Start from a color you already have — a logo color, a brand hex from your style guide — paste or type it into the base swatch, switch the harmony mode to complementary, and GenHub calculates the exact opposite hue at matching saturation and lightness. Lock your original color, reroll the complement a few times if the harmony mode offers variation, and check contrast before you commit to using it for text.
FAQ
Can I pick the base color?
Yes — edit any swatch's hex and reroll to build harmonies around your chosen base.
Does it check accessibility?
Yes. The contrast report shows AA/AAA levels for each color on white and black.
What's the difference between complementary and triadic?
Complementary uses two colors 180° apart on the wheel for maximum contrast; triadic uses three colors 120° apart, which is more varied but slightly less punchy than a straight complementary pair.
Can I lock the base color and only reroll the rest?
Yes — lock the swatch you want to keep and reroll; locked colors stay fixed while the harmony recalculates around them.
Is complementary the same as 'opposite' in every color system?
The exact opposite hue can shift slightly depending on whether a tool uses RYB, RGB or HSL color wheels — GenHub calculates it consistently in HSL space, which is the standard used across most modern design and CSS tooling.