Wondering for a while of how to apply some styling on cross-reference generated by addCrossReference(), I discovered that adding some options like 'bold' => 'true', 'color' => '#FF0000' actually worked!
But this is not documented in your API:
https://www.phpdocx.com/api-documentation/word-content/add-cross-reference-Word-document-with-PHP
Working example:
$wf->addCrossReference($refTitle, [
'type' => 'bookmark',
'referenceName' => $refTitle,
'bold' => true,
'color' => '#00FF00'
]);
You should indicate this on your API as it is really useful :)
Best regards,