java/com/google/lizlooney/shoppinglist/res/color/checkbox_theme.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:state_checked="false"
        android:color="#FF00FFFF"/>
  <item android:state_checked="true"
        android:color="#FF00FF00"/>
</selector>