Android: changing theme of tab widget indicator

Question

I'm having a problem changing the theme of my app, or changing some aspect of it. I don't as the documentation is saying, but it's not changing! Here is my code:

in

res/values/themes.xml:
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- the theme applied to the application or activity -->
    <style name="CustomActionBarTheme"
           parent="@android:style/Theme.Holo.Light.DarkActionBar">
        <item name="android:actionBarTabStyle">@style/MyActionBarTabs</item>
    </style>

    <!-- ActionBar tabs styles -->
    <style name="MyActionBarTabs"
           parent="@android:style/Widget.Holo.ActionBar.TabView">
        <!-- tab indicator -->
        <item name="android:background">#0033CC</item>
    </style>
</resources>

and in the Manifest file, I changed the app theme like this:

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/CustomActionBarTheme" >

...etc.

The tabs style don't change at all! note that I'm sure it takes the new theme because if I replaced the parent theme to:

parent="@android:style/Theme.Holo"

the whole theme changes!

So, what is the right way of changing the theme or some specific items of it? and that is the best place to learn more about android theming?