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.

Andrew Norcross

Reaktiv

The Reaktiv CSS Builder allows site owners to add custom CSS for any part of the site directly in the dashboard. Unlike other CSS builders, this plugin creates an actual CSS file and loads that instead of putting it all in the head, allowing the file to be cached.
Features
<ul>
<li>CSS editor contains live syntax highlighting</li>
<li>Multisite compatible</li>
<li>Import and export capabilities</li>
</ul>

Reaktiv CSS Builder

Add user generated custom CSS directly in the dashboard.

POFW Option CSS vs Reaktiv CSS Builder