There is another way to change the background color, however it is a hack and might fail on future versions of Android if the View hierarchy of the Window and its title is changed. However, the code won't crash, just miss setting the wanted color, in such a case.
In your Activity, like onCreate, do:
View titleView = getWindow().findViewById(android.R.id.title);
if (titleView != null) {
ViewParent parent = titleView.getParent();
if (parent != null && (parent instanceof View)) {
View parentView = (View)parent;
parentView.setBackgroundColor(Color.rgb(0x88, 0x33, 0x33));
}
}