How to highlight a page in the page list (Admin Menu)?

You can add a stylesheet for admin using the following code,

add this in function.php

function mmk_enqueue_custom_admin_style() {
            wp_register_style( 'pixel_admin_css', get_template_directory_uri() . '/admin.css', false, '1.0.0' );
            wp_enqueue_style( 'pixel_admin_css' );
        }
 

   add_action( 'admin_enqueue_scripts', 'mmk_enqueue_custom_admin_style' );

then add create admin.css in theme directory:
you can using following class to highlight

.row-title