Nick Halsey

WordPress core provides custom CSS functionality in the customizer that’s specific to the current theme; you can switch themes freely with each theme’s additional CSS remaining in place. Sometimes, you need some CSS to apply regardless of the current theme persistently. This plugin adds a plugin CSS option for CSS that’s global and persists across theme changes.
With the Customizer, your CSS is instantly live-previewed, offering the ability to see exactly how your site will look before you publish your changes. The plugin CSS option is stored as an <code>option</code>. Prior to WordPress 4.7 (which introduced additional CSS in core), theme-specific CSS was stored as a <code>theme_mod</code>, in 4.7 and newer this is migrated to the core CSS functionality (which is theme-specific).

Modular Custom CSS

WordPress core provides custom CSS functionality in the customizer that's specific to the current theme; you can switch themes freely with each t …

Pektsekye

This plugin requires <a href="https://wordpress.org/plugins/product-options-for-woocommerce/" rel="ugc">Simple Product Options for WooCommerce</a> plugin.
Allows to add custom CSS classes to product options. So you can apply specific style for certain product option or option value. 
Also another plugin or custom JS script can find that specific product option by CSS class.
You can check a demo on this page: 
<a href="http://hottons.com/demo/wp/ef/product/option-css/" rel="nofollow ugc">DEMO Page</a>
You can read the installation instructions here: 
<a href="http://hottons.com/demo/wp/ocss/README.html" rel="nofollow ugc">README</a>
Simple Code Idea:
The idea of this plugin is to keep the base version as simple as possible. 
And to add the new features as modifications.
This plugin has just 17 files to make it easy to use and customize. If you need more features check the modifications page <a href="http://hottons.com/ocss_modifications" rel="nofollow ugc">hottons.com/ocss_modifications</a>
Contact me by email <a href="mailto:pektsekye@gmail.com" rel="nofollow ugc">pektsekye@gmail.com</a> if you have questions or need help.
<h3>Translators</h3>
<h4>Available Languages</h4>
<ul>
<li>English (Default)</li>
</ul>
<h3>Documentation</h3>
Full documentation is available <a href="http://hottons.com/demo/wp/ocss/README.html" rel="nofollow ugc">here</a>.

POFW Option CSS

Adds custom CSS classes to product options of the "Product Options for WooCommerce" plugin.

Modular Custom CSS vs POFW Option CSS