session-android/res/drawable/recycler_view_fast_scroller_handle.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_selected="true">
        <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">
            <corners android:radius="2dp"/>
            <solid android:color="#FF0288D1"/>
            <size android:height="32dp" android:width="4dp"/>
        </shape>
    </item>
    <item>
        <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">
            <corners android:radius="2dp"/>
            <solid android:color="#FF737373"/>
            <size android:height="32dp" android:width="4dp"/>
        </shape>
    </item>
</selector>