Add new heading style for an outline

functions.php

<?php
/**
 * Block Styles
 *
 * @link https://developer.wordpress.org/reference/functions/register_block_style/
 *
 * @package WordPress
 * @subpackage HeaderOutline
 * @since HeaderOutline 1.0
 */

if ( function_exists( 'register_block_style' ) ) {
	/**
	 * Register block styles.
	 *
	 * @since HeaderOutline 1.0
	 *
	 * @return void
	 */
	function more_block_styles_register_block_styles() {

		// Headings
		register_block_style(
			'core/heading',
			array(
            			'name'          => 'outline-typo',
				'label'           => __( 'Outline Typo', 'more-block-styles' ),
            			'is_default'   => false,
				'inline_style' => '.wp-block-heading.is-style-outline-typo { 
					color: transparent;
					-webkit-text-stroke-width: 1px;
					-webkit-text-stroke-color: #333; // How do I get the real used current color from the block editor?
				}',
			)
		);

	}
	add_action( 'init', 'more_block_styles_register_block_styles' );
}