This is a simple Tailwind plugin to expose all of Tailwind's colors, including any custom ones, as custom css properties on the `:root` element.

There are a couple of main reasons this is helpful:

- You can reference all of Tailwind's colors—including any custom ones you define—from handwritten CSS code.
- You can define _all_ of your colors within the Tailwind configuration, and access the final values programmatically, which isn't possible if you did it the other way around: referencing custom CSS variables (defined in CSS code) from your Tailwind config.

See the [Tailwind Plugins](https://tailwindcss.com/docs/plugins) for more info on plugins.

```js
module.exports = {
  theme: {
    extend: {
      colors: {
        gray: {
          '100': '#f5f5f5',
          '200': '#eeeeee',
          '300': '#e0e0e0',
          '400': '#bdbdbd',
          '500': '#9e9e9e',
          '600': '#757575',
          '700': '#616161',
          '800': '#424242',
          '900': '#212121',
        },
      },
    },
  },
  plugins: [
    function({ addBase, theme }) {
      function extractColorVars(colorObj, colorGroup = '') {
        return Object.keys(colorObj).reduce((vars, colorKey) => {
          const value = colorObj[colorKey];

          const newVars =
            typeof value === 'string'
              ? { [`--color${colorGroup}-${colorKey}`]: value }
              : extractColorVars(value, `-${colorKey}`);

          return { ...vars, ...newVars };
        }, {});
      }

      addBase({
        ':root': extractColorVars(theme('colors')),
      });
    },
  ],
};
```