// Create tab
add_filter( \'woocommerce_product_data_tabs\', \'add_my_custom_product_data_tab\' , 99 , 1 );
function add_my_custom_product_data_tab( $product_data_tabs ) {
    $product_data_tabs[\'my-custom-tab\'] = array
    (
        \'label\' => __( \'XColor\', \'my_text_domain\' ),
        \'target\' => \'my_custom_product_data\',
    );
    return $product_data_tabs;
}
// Create field
add_action( \'woocommerce_product_data_panels\', \'add_my_custom_product_data_fields\' );
function add_my_custom_product_data_fields() {
    global $woocommerce, $post;
    ?>
    <!-- id below must match target registered in above add_my_custom_product_data_tab function -->
    <div id="my_custom_product_data" class="panel woocommerce_options_panel">
        <?php
        woocommerce_wp_text_input(
            array(
                \'id\'          => \'xcolor_html\',
                \'label\'       => __( \'HTML\', \'woocommerce\' )
            ));
        ?>
    </div>
    <?php
}
// Save field content - this don\'t work =(( white page
function woo_add_custom_general_fields_save( $post_id )
{
    // Text Field
    $woocommerce_text_field = $_POST[\'xcolor_html\'];
    if (!empty($woocommerce_text_field))
        update_post_meta($post_id, \'xcolor_html\', esc_attr($woocommerce_text_field));
}
// Show field content on product page
add_action( \'woocommerce_single_product_summary\', \'woocommerce_xcolor\', 15 );
function woocommerce_xcolor(){
    echo get_post_meta( get_the_ID(), \'xcolor_html\', true );
}