res/drawable/circle_background.xml

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true">
        <shape android:shape="oval">
            <size android:width="48dp" android:height="48dp"/>
            <stroke android:width="0dp" android:color="#FFBBBBBB" />
            <solid android:color="#D05555FF" />
        </shape>
    </item>
    <item>
        <shape android:shape="oval">
            <size android:width="48dp" android:height="48dp"/>
            <stroke android:width="0dp" android:color="#FFBBBBBB" />
            <solid android:color="#665555FF" />  <!-- spec is 26000000 -->
        </shape>
    </item>


</selector>