java/com/android/incallui/commontheme/res/drawable/answer_decline_background.xml

<?xml version="1.0" encoding="utf-8"?>
<ripple xmlns:android="http://schemas.android.com/apk/res/android"
  android:color="#80FFFFFF">
  <item>
    <shape
      android:shape="oval">
      <solid android:color="#DF0000"/>
    </shape>
  </item>
</ripple>