styles.xml

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.DayNight.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>

        <item name="android:windowNoTitle">true</item>
        <item name="android:windowActionBar">false</item>
        <item name="android:windowFullscreen">true</item>
        <item name="android:windowContentOverlay">@null</item>
    </style>

    <style name="Divider">
        <item name="android:background">?android:attr/listDivider</item>
        //you can give your color here. that will change all divider color in your app.
    </style>

    <style name="Divider.Horizontal" parent="Divider">
        <item name="android:layout_width">match_parent</item>
        <item name="android:layout_height">1dp</item>
        // You can change thickness here.

    </style>

</resources>