guide_radio_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_checked="false">
        <shape android:shape="oval">
            <solid android:color="@color/black" />
            <size android:width="15dp" android:height="15dp" />
        </shape>
    </item>

    <item android:state_checked="true">
        <shape android:shape="oval">
            <solid android:color="@color/teal_200" />
            <size android:width="15dp" android:height="15dp" />
        </shape>
    </item>

</selector>