How to override wp-admin styling
As noted by @Fusion, this has changed beginning with version 5. In order to override admin styles for 5.*, you need a hook in functions.php, something like this: function custom_admin() { $url = get_settings(‘siteurl’); $url = $url . ‘/wp-content/themes/my-theme/wp-admin.css’; echo ‘<link rel=”stylesheet” type=”text/css” href=”‘ . $url . ‘” />’; } add_action(‘admin_head’, ‘custom_admin’) Sources: WordPress Codex … Read more