How do I separate my theme’s styles from editor styles?

The WordPress editor shouldn’t be pulling in the themes CSS files unless you have a file that is named editor-style.css. You can either use the editor-style.css and simply place it in your themes root directory, add certain styles to the stylesheet (not all the theme div and id tags will apply to the WordPress Editor).

Another way to do it is to use wp_enqueue_script to enqueue a CSS file with whatever name you wish, or in a different file location other than the themes root directory. Some authors use this method to minimize the amount of files that live in the theme root directory.

If your theme is incorrectly registering or enqueueing a script it can cause the files to be loaded into the WordPress admin area. Let me know what your theme is using for the editor stylesheet if this doesn’t help so I can give you better assistance.