How can I change separator color in NavigationView?

I'm trying to use NavigationView to implement NavigationDrawer. I have added the separator by setting group id in menu. However I can't see the separator. I guess it is because the separator color is same as the background. So I want to change the separator color. But I find no way to change it. Can anyone help me?

In screenshot, it seems have a room for separator between History and Settings, but you can't see it.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:fitsSystemWindows="true"
    tools:context=".ui.MapActivity">

    <LinearLayout
        android:id="@+id/main_content"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <include layout="@layout/toolbar_actionbar" />

        <!--main content-->
    </LinearLayout>

    <android.support.design.widget.NavigationView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@color/navdrawer_background"
        app:insetForeground="#4000"
        app:itemTextColor="@color/navdrawer_item_text_color"
        app:itemIconTint="@color/navdrawer_item_icon_tint"
        app:headerLayout="@layout/drawer_header"
        app:menu="@menu/drawer"/>
</android.support.v4.widget.DrawerLayout>

drawer.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <group android:id="@+id/group_feature"
        android:checkableBehavior="single">
        <item android:id="@+id/navdrawer_item_map"
            android:checked="true"
            android:icon="@drawable/ic_drawer_map"
            android:title="@string/navdrawer_item_map"/>
        <item android:id="@+id/navdrawer_item_favourite"
            android:icon="@drawable/ic_drawer_fav"
            android:title="@string/navdrawer_item_fav"/>
        <item android:id="@+id/navdrawer_item_history"
            android:icon="@drawable/ic_drawer_history"
            android:title="@string/navdrawer_item_history"/>
    </group>
    <group android:id="@+id/group_settings"
        android:checkableBehavior="single">
        <item android:id="@+id/navdrawer_item_settings"
            android:icon="@drawable/ic_drawer_settings"
            android:title="@string/navdrawer_item_settings"/>
        <item android:id="@+id/navdrawer_item_help"
            android:icon="@drawable/ic_drawer_help"
            android:title="@string/navdrawer_item_help"/>
        <item android:id="@+id/navdrawer_item_about"
            android:icon="@drawable/ic_drawer_about"
            android:title="@string/navdrawer_item_about"/>
    </group>
</menu>

just apply following line on style.xml

<item name="android:listDivider">your_color</item>

The below is just information for your knowledge ... If you have seen design support library .. they are using following layout for NavigationView seprator..

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
             android:layout_width="match_parent"
             android:layout_height="wrap_content">

    <View android:layout_width="match_parent"
          android:layout_height="1dp"
          android:background="?android:attr/listDivider"/>

</FrameLayout>

here, you can see android:background="?android:attr/listDivider" .. So enjoy ... and here is my output that i change color to holo_blue