<resources>
    <style name="MyCustomTheme" parent="@android:style/Theme.Holo.Light">
        <item name="android:actionBarStyle">@style/MyActionBarTheme</item>
    </style>

    <style name="MyActionBarTheme" parent="@android:style/Widget.Holo.Light.ActionBar">
        <item name="android:background">ANY_HEX_COLOR_CODE</item>
    </style>
</resources>

ActionBar actionBar = getActionBar();
actionBar.setBackgroundDrawable(new ColorDrawable(Color.RED)); // set your desired color