I'm not an Android expert, but I wanted to use the Android Holo Light theme, and changing my <application> tag in my Android application manifest file to look like this definitely switched my Android app from having a dark background to a light background:
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/android:Theme.Holo.Light">
That last line of code where I set the "theme" is what did the trick for me.
If only I could take a screenshot on my Android tablet, I'd be glad to show you the before and after pictures, but without this tag my application -- which primarily uses ListActivity's and Fragments -- had light text on a dark background, but with this setting, it now has dark text on a light background.
Update: I have learned that you can't do this for all Android apps. In particular, you can't use this when you're using an ActionBarActivity; it requires that you use some "compatibility" themes.
