zumo_2.0_android/app/src/main/res/drawable/tab_white_active.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item>
  <shape
    android:innerRadius="0dp"
    android:shape="ring"
    android:thickness="3dp"
    android:useLevel="false">
    <solid android:color="@color/CFFFFFF"/>
  </shape>
</item>
</layer-list>