Adds some useful classes to the WooCommerce layered navigation widget. This makes it very easy to stylise attribute colours or anything that can be represented with an icon.

woocommerce_layered_navigation_add_classes.php

<?php

/**
 * Adds some useful classes to the WooCommerce layered navigation widget.
 * This makes it very easy to stylise attribute colours or anything that can be represented with an icon.
 *
 * @param string $term_html - the item html
 * @param object $term - the item props
 *
 * @return string - the old html list content wrapped inside a div with as class term id, term name and taxonomy
 */
add_filter( 'woocommerce_layered_nav_term_html', 'my_layered_nav_html_filter', 10, 2 );
function my_layered_nav_html_filter( $term_html, $term ){
    return sprintf('<div class="%s %s %s">%s</div>',
        "term-".$term->term_id,
        "term-".$term->slug,
        "tax-".$term->taxonomy,
        $term_html
    );
}