metamask-extension/.storybook/metamask-storybook-theme.js

// .storybook/YourTheme.js

import { create } from '@storybook/theming';

export default create({
  base: 'light',
  brandTitle: 'MetaMask Storybook',

  // Typography
  fontBase: "'Avenir Next', -apple-system, BlinkMacSystemFont, sans-serif",
  fontCode: 'Inconsolata, monospace',
});