Add a Different CSS Class Into The Body Tag of Different WP Pages

In your functions.php:

function my_body_class($classes) {

    if(is_page()){
      global $page;
      $title = get_the_title(  $page );
      $classes[] = $title;

    }
    return $classes;
}

add_filter('body_class', 'my_body_class');

That will add the page title as a class to each page.