WooCommerce Related Products by Attribute

Disable default Related Products and try this (Add custom code to the functions.php)

add_action( 'woocommerce_after_single_product_summary', 'custom_output_product_collection', 12 );
function custom_output_product_collection(){

    ## --- YOUR SETTINGS --- ##

    $attribute = "attribute_slug"; // <== HERE define your attribute slug
    $limit     = "5";     // <== Number of products to be displayed
    $cols      = "5";     // <== Number of columns
    $orderby   = "rand";  // <== Order by argument (random order here)

    ## --- THE CODE --- ##

    global $post, $wpdb;

    // Formatting the attribute
    $attribute = sanitize_title( $attribute );
    $taxonomy  = 'pa_' . $attribute;

    // Get the WP_Term object for the current product and the defined product attribute
    $terms = wp_get_post_terms( $post->ID, $taxonomy );
    $term = reset($terms);

    // Get all product IDs that have  the same product attribute value (except current product ID)
    $product_ids = $wpdb->get_col( "SELECT DISTINCT tr.object_id
        FROM {$wpdb->prefix}term_relationships as tr
        JOIN {$wpdb->prefix}term_taxonomy as tt ON tt.term_taxonomy_id = tr.term_taxonomy_id
        JOIN {$wpdb->prefix}terms as t ON tt.term_id = t.term_id
        WHERE tt.taxonomy LIKE '$taxonomy' AND t.term_id = '{$term->term_id}' AND tr.object_id != '{$post->ID}'" );

    // Convert array values to a coma separated string
    $ids = implode( ',', $product_ids );

    ## --- THE OUTPUT --- ##

    echo '<section class="'.$attribute.' '.$attribute.'-'.$term->slug.' products">
        <h2>'.__( "Collection", "woocommerce" ).': '.$term->name.'</h2>';

    echo do_shortcode("[products ids="$ids" columns="$cols" limit="$limit" orderby='$orderby']");

    echo '</section>';
}