Telegram / TMessagesProj / src / main / res / drawable / switch_thumb.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_checked="true" android:drawable="@drawable/switch_to_on2" />
    <item android:drawable="@drawable/switch_to_on1" />
</selector>