Leonardo

Free plan APIWeb

What Leonardo is

Leonardo is a color system tool for designing user interfaces and data visualizations. It creates, manages, and shares color themes, with swatches generated from target contrast ratios or defined by target lightness. Adaptive themes provide controls for brightness, contrast, and saturation. For data visualization, it offers sequential and diverging scales. Accessibility tools cycle through colors for colorblind-safe palettes and compare color differences across types of color vision deficiency. Its web application includes charts and 3D models for evaluating themes.

Themes and color scales can be downloaded as SVG files, and scales can also be exported as Tableau XML. Output for developers includes parameters for @adobe/leonardo-contrast-colors, CSS custom properties, and design tokens. The JavaScript package generates adaptive, contrast-based colors and can be installed with npm; its documentation includes vanilla JavaScript and React examples. The site also documents an MCP server for generating themes, checking contrast, converting colors, and creating palettes. Leonardo is free and open source under the Apache V2 license, with web and API platforms. Its generated contrast ratios may end up slightly above the requested value because of RGB color availability and color-space interpolation.

Who it suits

Leonardo suits designers and engineers building color scales for user interfaces, as well as people creating palettes for data visualization. It is also relevant to developers who want theme output as CSS properties, design tokens, or JavaScript package parameters.

What it does well

Generates swatches from target contrast ratios or target lightness.
Adaptive themes adjust brightness, contrast, and saturation.
Includes sequential and diverging scales for data visualization.
Checks color differences across color vision deficiency types.
Exports themes and scales as SVG and Tableau XML.
Free and open source under Apache V2.

What to know first

Generated contrast ratios may slightly exceed the requested values.
The JavaScript package is installed with npm.

Limits

Generated contrast ratios may be slightly higher than requested because available RGB colors and color-space interpolation constrain exact values.

Plans

Plan	Billed and limits	Price
Free / open source	No paid plans or usage limits are stated on the opened pages	Free

As leonardocolor.io lists them, read 9 Oct 2026. The maker's own page has the final word.

Getting started

Open the Leonardo website in a web browser.
Use the web application to create themes and color scales.
Set swatches by target contrast ratio or target lightness.
Adjust brightness, contrast, and saturation for adaptive themes.
Install @adobe/leonardo-contrast-colors with npm to generate adaptive contrast-based colors in JavaScript.

Verdict

Choose Leonardo to create and evaluate accessible color themes, particularly when you need contrast-based swatches, data visualization scales, or developer-ready output. Its free, open-source offering includes web and API access. Keep in mind that generated contrast ratios can be slightly higher than requested.

Questions

How much does Leonardo cost?

Leonardo is free, with a listed price of $0 plan.

Is Leonardo open source?

Yes. The project is licensed under Apache V2.

What platforms does Leonardo support?

The listed platforms are web and API.

What can I export from Leonardo?

Themes and scales can be downloaded as SVG, and scales can also be exported as Tableau XML. Developer output includes CSS custom properties and design tokens.

Does Leonardo have a JavaScript package?

Yes. @adobe/leonardo-contrast-colors can generate adaptive contrast-based colors and is installed with npm. Its documentation includes vanilla JavaScript and React examples.

What limitation should I consider when setting a contrast ratio?

Generated ratios may be slightly higher than requested because available RGB colors and color-space interpolation limit exact values.

Facts from Leonardo's own pages

Adaptive themes: Adaptive themes let users adjust brightness, contrast, and saturation. · leonardocolor.io, 9 Oct 2026
AI tooling: The site documents an MCP server with tools to generate themes, check contrast, convert colors, and create palettes. · leonardocolor.io, 9 Oct 2026
Audience: The project describes its web application as a collaborative tool for designers and engineers building color scales for user interfaces. · github.com, 9 Oct 2026
Color accessibility: The tools can cycle through colors for colorblind safe palettes and compare color difference across color vision deficiency types. · leonardocolor.io, 9 Oct 2026
Color analysis: The web application includes charts and 3D models for evaluating color themes. · leonardocolor.io, 9 Oct 2026
Contrast based colors: It generates color swatches from target contrast ratios and also lets users define swatches by target lightness. · leonardocolor.io, 9 Oct 2026
Data visualization: Leonardo offers sequential and diverging color scales for data visualization. · leonardocolor.io, 9 Oct 2026
Developer output: Theme output includes parameters for @adobe/leonardo-contrast-colors, CSS custom properties, and design tokens. · leonardocolor.io, 9 Oct 2026
Exports: Themes and color scales can be downloaded as SVG files, and the tool offers Tableau XML and SVG exports for scales. · leonardocolor.io, 9 Oct 2026
Integrations: The package documentation includes examples for vanilla JavaScript and React, and the homepage says its output can be copied into design tools. · leonardocolor.io, 9 Oct 2026
JavaScript package: The @adobe/leonardo-contrast-colors package can generate adaptive contrast-based colors and is installed with npm. · leonardocolor.io, 9 Oct 2026
License: The project is licensed under Apache V2. · github.com, 9 Oct 2026
Limit: Generated contrast ratios may be slightly higher than the requested ratio because available RGB colors and color space interpolation constrain exact values. · leonardocolor.io, 9 Oct 2026
Purpose: Leonardo creates, manages, and shares accessible color systems for user interface design and data visualization. · leonardocolor.io, 9 Oct 2026

Where Leonardo stands on Freedom251

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