Appends user role and id to the body classes for for front and backend in wordpress. Place this in a functionality plugin or functions.php file in the theme.

add_helpful_user_classes.php

function add_helpful_user_classes() {
	if ( is_user_logged_in() ) {
		add_filter('body_class','class_to_body');
		add_filter('admin_body_class', 'class_to_body_admin');
	}
}
add_action('init', 'add_helpful_user_classes');

/// Add user role class to front-end body tag
function class_to_body($classes) {
	global $current_user;
	$user_role = array_shift($current_user->roles);
	$classes[] = $user_role.' ';
	return $classes;
}

/// Add user role class and user id to front-end body tag

// add 'class-name' to the $classes array
function class_to_body_admin($classes) {
	global $current_user;
	$user_role = array_shift($current_user->roles);
	/* Adds the user id to the admin body class array */
	$user_ID = $current_user->ID;
	$classes .= $user_role.' '.'user-id-'.$user_ID ;
	return $classes;
	return 'user-id-'.$user_ID;
}

This goes well for the backend with adding custom css to the backend:
https://css-tricks.com/snippets/wordpress/apply-custom-css-to-admin-area/