The support link and its can be edited from the CMS section of the admin.
The login and register links are edited from:
webassist/plugins/headerlinks/headerlinks.php
I'd suggest downloading and using firebug to help determine what .css needs to be changed. Most will be located in the folder webassist/Themes/[YourThemeName]/CSS
Firebug will be a great resource to determine where and what to update.