BayernMessenger/vector/src/main/res/drawable/fg_group_item.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_selected="true">
        <shape android:shape="oval">
            <solid android:color="@android:color/transparent" />
            <stroke android:width="3dp" android:color="@color/pale_teal" />
        </shape>

    </item>
    <item android:drawable="@android:color/transparent" />

</selector>