Android: default AppTheme background colors
Check out this colors.xml file. If you do a Ctrl-F for "backround_holo_dark"
you can find the hex code. All the other holo theme colors are there as well. Enjoy!
<drawable name="screen_background_holo_light">#fff3f3f3</drawable>
<drawable name="screen_background_holo_dark">#ff000000</drawable>
<color name="background_holo_dark">#ff000000</color>
<color name="background_holo_light">#fff3f3f3</color>
You can use your theme's default background color by referencing the attribute:
?android:colorBackground