$patterns = array(
		'`\<strong\>(.+?)\</strong\>`is',
		'`\<em\>(.+?)\</em\>`is',
		'`\<u\>(.+?)\</u\>`is',
		'/<span style=\"color: ([#a-z\d]+);\">(.+)<\/span>/i'
       );
	//<span style="color: navy;">
	$replaces =  array(
        '[b]\\1[/b]',
        '[i]\\1[/i]',
		'[u]\\1[/u]',
		'[color=\\1]\\2[/color]'
        );
	
	$string = preg_replace($patterns, $replaces , $string);