Change shape in layer-list programatically

i have this drawable file :

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://ift.tt/nIICcg">

    <item
        android:left="6dp"
        android:right="6dp"
        android:top="6dp"
        android:bottom="6dp"

        >
        <shape android:shape="oval">
            <size android:width="170dp"
                android:height="170dp"/>
            <solid android:color="@color/primaryColor"/>
        </shape>
    </item>

    <item
        android:left="18dp"
        android:right="18dp"
        android:top="18dp"
        android:bottom="18dp">

        <shape android:shape="oval" >
            <size android:width="140dp"
                android:height="140dp"/>
            <solid android:color="#EEEEEE"/>
        </shape>
    </item>


    <item
        android:left="30dp"
        android:right="30dp"
        android:top="30dp"
        android:bottom="30dp">

        <shape android:shape="oval" >
            <size android:width="140dp"
                android:height="140dp"/>
            <solid android:color="@color/primaryColor"/>
        </shape>
    </item>


</layer-list>

and i want to change the shape of only one oval programatically but i found nothing do to this.I want to change only one shape not all at the same time.

I made lot of research but nothing explain how to do this.

So please help me