Upgrade to CAM v8.1 or higher which provides better support and documentation for customization's. Refer to the Overview, Upgrading and Changing text sections of the Advanced Customization guide.
We recommend backing up and reverting all changes made manually and upgrading to CAM v8.1 before making further changes.You can also delete the files that were customized and run a repair to restore the defaults.
For customization's already made manually to the Home Realm Discovery page customers should look at the URL when they load the HRD page; it will be one of these files (probably WSFed):
C:\program files\Dell\Cloud Access Manager\RPSTS\<WSFed|SAML2|Oauth2>\UserIdentity.aspx
(you can see which css files that files link to in the head of each file).
For making customization's to the user login page look at:
C:\program files\Dell\Cloud Access Manager\Dell STS\style.css