13 Changing the Login Page skin
Because a different skin might be associated with each user's account, there is no way to know which skin should be shown on the ZWC login page. For this reason, the login page always comes up with the "beach" skin for all users.
To change the appearance of the login page, make changes directly to the "beach" skin, in the folder .../zimbra/skins/beach/. Simply make any logo or color changes you like to the .../zimbra/skins/beach/skin.properties file and it will show those changes on the login screen for all users. Also, as "beach" is the default skin for new users, this will also customize the skin that most of your users will see after login as well.
Unfortunately, changes you make to the "beach" skin will not necessarily survive upgrades to your ZWC install, as the new version will often change the default skins. To make sure your login skin survives upgrades, copy the "beach" skin into another directory before installing the upgrade, then replace the upgraded "beach" with the copy you just made.