material-dialogs/commons/src/main/res/drawable/gray_circle.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">
    <solid android:color="#BCBCBC" />
    <size
        android:width="@dimen/md_simplelist_icon"
        android:height="@dimen/md_simplelist_icon" />
</shape>