Hi,
I've got your link. It seems that the view displaying that element has been modified by your template to add extra classes to handle the coloring. If that's the case, you can rename the file templates/YOUR_TEMPLATE/html/com_hikashop/checkout/login.php via FTP in order to deactivate the override.
Otherwise, modifying the CSS of the template would also be a solution but you should seek advice with your template provider.
Also note that there are several javascript errors on the pages:
take.ms/wMXxy
These also come from the template javascript files and prevent the switcher to actually work on your website (regardless of what you select in it, you always see the login form). You should also seek advice wih your template provider for help fixing these javascript errors.