In this mod the asterisks are defined in includes/languages/english/extra_definitions/referral_defines like this:
define('ENTRY_SOURCE_TEXT', '*');
define('ENTRY_SOURCE_OTHER_TEXT', '*');
In tpl_modules_create_account.php ENTRY_SOURCE_TEXT and ENTRY_SOURCE_OTHER_TEXT both have been given the class <span class="inputRequirement">
Try changing class="inputRequirement" to class="alert"
Glad to help
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