Add custom body class to specific templates.
See – https://www.billerickson.net/wordpress-class-body-tag/
<?php
/**
* Portfolio Archive Body Class
* @author Bill Erickson
* @link http://www.billerickson.net/wordpress-class-body-tag/
*
* @param array $classes, existing body classes
* @return array $classes
*/
function be_portfolio_archive_body_class( $classes ) {
$classes[] = 'portfolio-archive';
return $classes;
}
add_filter( 'body_class', 'be_portfolio_archive_body_class' );