I would start with a Google page in the Styles and Themes section. Many of your questions have been answered.
http://developer.android.com/guide/topics/ui/themes.html
Here is a simple tutorial:
http://developerlife.com/tutorials/?p=309
EDIT:
If you talk about phones instead of the application, you can create themes for specific notes on the main screen, for example aHome . I am sure that if you look around your site, you will see how to create a theme for your application.
There are also sites like Android themes , but they require you to root your phone and install a custom ROM such as Cyanogen.
Perhaps you can also write your own custom screen.
Jay Askren Apr 10 '10 at 13:42
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