delwinv

A very tiny plugin that adds the ACF field key, field name, Flexible Content field name and Flexible Content layout name to the WYSIWYG 
editor body tag, allowing you to target these classes, along with the existing post-type-* classes added by default by WordPress, in 
your editor-style.css for a better admin/editor experience.
This works for both ACF and ACF Pro, version 5.
<h3>Usage</h3>
<ol>
<li>Install the plugin through the Install Plugins interface or by uploading the <code>acf-plugin-wysiwyg-styling</code> folder to your <code>/wp-content/plugins/</code> directory.</li>
<li>Activate the ACF WYSIWYG Styling plugin from the Admin > Plugins menu.</li>
<li>Create or edit your editor-style.css in your theme directory and use the newly added classes to style your WYSIWYG editors.</li>
</ol>
For example:
<ul>
<li>
The ACF WYSIWYG field with key field_9999ffff11112222 can be targeted with the following CSS:
body.acf-field-key-field_9999ffff11112222 { 
 background-color: red; 
}
</li>
<li>
The ACF WYSIWYG field with key field_9999ffff11112222 in the “room” post type can be targeted with the following CSS:
body.post-type-room.acf-field-key-field_9999ffff11112222 { 
 background-color: blue; 
}
</li>
<li>
All ACF WYSIWYG fields named “my_wysiwyg” can be targetted with the following CSS:
body.acf-field-name-my_wysiwyg { 
 background-color: yellow; 
}
</li>
<li>
All ACF WYSIWYG fields in the Flexible Content field named “page_content” can be targetted with the following CSS:
body.acf-flex-name-page_content { 
 color: green; 
}
</li>
<li>
All ACF WYSIWYG fields in the Flexible Content layout field named “test_layout” can be targetted with the following CSS:
body.acf-layout-test_layout { 
 font-family: “Computer Modern Serif”; 
}
</li>
<li>
The ACF WYSIWYG field named “my_wysiwyg” in the Flexible Content layout field named “test_layout” can be targetted with the following CSS:
body.acf-layout-test_layout.acf-field-name-my_wysiwyg { 
 border: 4px solid red; 
 height: 100%; 
 margin: 0 auto; 
 max-width: 100px; 
}
</li>
</ul>
N.B. I target using the body tag so that a user cannot accidentally target the admin CSS in their edit of the field (regardless of how unlikely 
that would be).

ACF WYSIWYG Styling

Provides the necessary CSS classes in ACF WYSYWIG editor to allow for complete styling of the admin interface.

benallfree

Lesser helps you manage custom CSS for your site using <a href="http://lesscss.org" rel="nofollow ugc">LESS</a>. Lesser is compatible with all WordPress caching because Lesser uses WordPress’s built-in script management features to output the final CSS.
Lesser keeps your custom styling out of your themes and plugins. That means theme and plugin updates and changes won’t overwrite your LESS. You can even switch themes and add/remove plugins without fear of losing the custom responsive CSS styling you worked so hard to debug on all the mobile device formats.
Benefits:
<ul>
<li>Independent of any WordPress theme or plugin</li>
<li>Switch themes without losing custom styling</li>
<li>Add/Remove plugins without losing custom styling</li>
<li>Efficiently organize CSS</li>
<li>Ideal for managing responsive design customizations</li>
</ul>
Features:
<ul>
<li>Use LESS instead of CSS</li>
<li>Edit directly from your admin</li>
<li>Compatible with popular WordPress caching extensions</li>
<li>Easily migrate your changes using popular plugins like <code>WP Clone</code></li>
<li>Fast – Lesser compiles your LESS once and saves the result for super-fast load times</li>
</ul>
<a href="http://wp-results.com/plugins/lesser" rel="nofollow ugc">Lesser Pro</a> adds the following features:
<ul>
<li>Separate editors for both admin and public CSS changes, as well as changes common to both</li>
<li>Minification – speed up your production site with compact files</li>
<li>Test mode – expanded CSS output and cache-busting for easy development even through caching proxies</li>
</ul>

Lesser

Lesser helps you manage custom CSS for your site using LESS. Lesser is compatible with all WordPress caching because Lesser uses WordPress's buil …

ACF WYSIWYG Styling vs Lesser