packages/local_auth/local_auth_android/android/src/main/res/drawable/fingerprint_initial_icon.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
  <item>
    <shape android:shape="oval">
      <solid android:color="#607D8B"/>
      <size
          android:width="40dp"
          android:height="40dp"/>
    </shape>
  </item>
  <item android:drawable="@drawable/ic_fingerprint_white_24dp"
      android:bottom="8dp"
      android:left="8dp"
      android:right="8dp"
      android:top="8dp"/>
</layer-list>