want action bar becomes transparent but becomes grey

Question

i want to change my action bar background to become tranparent but not overlay, because i want to make my action bar get its backround from activity background and just have border-bottom to separate it from activity . i have try to make custom style with action bar background transparent but its become gray.

this is my custom style

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- the theme applied to the application or activity -->
    <style name="CustomActionBarTheme"
        parent="@style/Theme.AppCompat.Light.DarkActionBar">
        <item name="android:actionBarStyle">@style/MyActionBar</item>
        <item name="android:actionMenuTextColor">@color/putih</item>
        <item name="android:homeAsUpIndicator">@drawable/navigation_previous_item</item>
        <!-- Support library compatibility -->
        <item name="actionBarStyle">@style/MyActionBar</item>
        <item name="actionMenuTextColor">@color/putih</item>
        <item name="homeAsUpIndicator">@drawable/navigation_previous_item</item>
    </style>

    <!-- ActionBar styles -->
    <style name="MyActionBar"
        parent="@style/Widget.AppCompat.ActionBar">
        <item name="android:background">@android:color/transparent</item>

        <item name="android:titleTextStyle">@style/MyActionBarTitleText</item>

        <!-- Support library compatibility -->
        <item name="background">@android:color/transparent</item>
        <item name="titleTextStyle">@style/MyActionBarTitleText</item>
    </style>

    <!-- ActionBar title text -->
    <style name="MyActionBarTitleText"
        parent="@style/TextAppearance.AppCompat.Widget.ActionBar.Title">
        <item name="android:textColor">@color/putih</item>
        <!-- The textColor property is backward compatible with the Support Library -->
    </style>

</resources>

Thank for your help