Why build your own

Each theme's theme.min.css is a drop-in replacement for Bulma — no build step required. If you want to override a theme's tokens (colours, radii, etc.) rather than just load it as-is, you need the theme's Sass source instead, compiled in your own project.

Get the source

Every theme publishes its _variables.scss — the file that defines its Sass tokens ($primary-h, $radius-medium, and so on) — right next to its compiled CSS:

/dist/<slug>/theme.min.css
/dist/<slug>/_variables.scss

Download the one for the theme you're starting from (see that theme's page) and add it to your own project.

Wire it into Bulma

_variables.scss only defines tokens and a variables mixin — it doesn't pull in Bulma itself. In your own project, with bulma installed as a dependency, write an entry file that combines the two:

@use "_variables" as v with (
  $primary-h: 210,
  $primary-s: 55%,
  $primary-l: 28%,
);
@use "bulma/sass" as bulma with (
  $custom-colors: v.$custom-colors
);

:root {
  @include v.variables;
}

• @use "_variables" as v with (...) loads the downloaded file and overrides whichever tokens you want to change — omit the with (...) block entirely to keep the theme's defaults.
• @use "bulma/sass" as bulma with ($custom-colors: v.$custom-colors) brings in Bulma itself, configured with the theme's secondary colour (see Color Palette for what that adds).
• :root { @include v.variables; } emits the theme's --bulma-* custom properties.

Compile the entry file with your own Sass toolchain (sass, Vite, webpack + sass-loader, …) — any setup that resolves bulma/sass through your project's node_modules will work.

This is the same composition the library uses internally to build theme.min.css, just written for a normal Sass project instead of using this repository's build script.