storybook/docs/_snippets/storybook-preview-global-parameters.md

export default {
  parameters: {
    backgrounds: {
      values: [
        { name: 'red', value: '#f00' },
        { name: 'green', value: '#0f0' },
      ],
    },
  },
};

// Replace your-framework with the framework you are using (e.g., react, vue3)
import { Preview } from '@storybook/your-framework';

const preview: Preview = {
  parameters: {
    backgrounds: {
      values: [
        { name: 'red', value: '#f00' },
        { name: 'green', value: '#0f0' },
      ],
    },
  },
};

export default preview;