Telephone Numbers show as grey link link color as background in iphone

I need the numbers to show as white please see http://www.psweb-design.com

I have read in support that you can add custom code to child functions.php file which I have done :

function add_custom_code(){
$output = “<meta name=’format-detection’ content=’telephone=no’>”;
return $output;
}
add_action(‘wp_head’, ‘add_custom_code’);

I am afriad I am unclear what to do now do I need to add some css? can you please help

Pete