Google Stitch's skill that pulls a DESIGN.md with tokens, components and patterns out of any frontend codebase. Works without Stitch.
Expo's official guide to a token-based design system of color, spacing and type inside an Expo app.
Ten ready font and color themes for slides, documents and HTML pages, or a custom theme generated on the spot.
MUI's official guidance on theming: createTheme, palette, color schemes, CSS variables and dark mode.