An example of how to add the EE terms to the body_class

functions.php

<?php //Please do not add the opening PHP tag if you already have one

function tw_ee_taxonomy_in_body_class( $classes ){
  //Check if within a single EE event post.
  if( is_singular( 'espresso_events' ) ) { 
    //Pull the terms used for the Event.
    $custom_terms = get_the_terms( 0, 'espresso_event_categories' );
    
    //If we have custom terms, add them to the body class
    if ( $custom_terms ) {
      
      foreach ( $custom_terms as $custom_term ) {
        //Add each term slug to the body class with the prefix 'category-'
        $classes[] =  'category-' . $custom_term->slug;
      }
    }
  }
  //Return the body classes
  return $classes;
}
add_filter( 'body_class', 'tw_ee_taxonomy_in_body_class' );