Changing background color of AlertDialog

Question

I was able to change background for regular Dialog quite easily, and now I want to assign my specific background color to AlertDialog as well. I have extracted the necessary pieces from android-17/styles.xml (the pieces I couldn't reference to simply subclass) and successfully altered button box bg color:

<!--    Extracted from styles.xml for Holo theme   -->

    <style name="AlertButtonBarWithBackground" parent="@android:style/Holo.ButtonBar.AlertDialog">
        <item name="android:background">@color/dialog_background_color</item>        
    </style>

    <style name="AndroidHoloTextAppearance">
        <item name="android:textColor">?android:attr/textColorPrimary</item>
        <item name="android:textColorHighlight">?android:attr/textColorHighlight</item>
        <item name="android:textColorHint">?android:attr/textColorHint</item>
        <item name="android:textColorLink">?android:attr/textColorLink</item>
        <item name="android:textSize">18sp</item>
        <item name="android:textStyle">normal</item>
    </style>

    <style name="AndroidDialogWindowTitle">
        <item name="android:maxLines">1</item>
        <item name="android:scrollHorizontally">true</item>
        <item name="android:textAppearance">@android:style/TextAppearance.DialogWindowTitle</item>
    </style>

    <style name="AndroidDialogWindowTitle.Holo">
        <item name="android:maxLines">1</item>
        <item name="android:scrollHorizontally">true</item>
        <item name="android:textAppearance">@style/AndroidHoloTextAppearance</item>
    </style>

    <style name="AlertDialogTheme" parent="@android:style/Theme.Holo.Dialog">
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:windowTitleStyle">@style/AndroidDialogWindowTitle.Holo</item>
        <item name="android:windowContentOverlay">@null</item>
        <item name="android:windowMinWidthMajor">@android:dimen/dialog_min_width_major</item>
        <item name="android:windowMinWidthMinor">@android:dimen/dialog_min_width_minor</item>
        <item name="android:buttonBarStyle">@style/AlertButtonBarWithBackground</item>
    </style>

<!--    End of extracted fragment  -->

    <style name="ActivityTheme" parent="android:Theme.Holo">
        <item name="android:alertDialogTheme">@style/AlertDialogTheme</item>
    </style>

But no matter how I try altering text area background, the background of a shadow around dialog's perimeter is also altered. This is not the case with a regular Dialog, for which I've set bg color as follows:

@color/dialog_background_color

It still has the nice standard shadow, unaltered by the bg color, so I believe this can be done for alert dialog as well?..