btn_blue.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape>
            <solid android:color="@color/btn_blue" />
            <corners android:radius="@dimen/btn_blue_radius"/>
        </shape>
    </item>
    <item
        android:bottom="2px"
        android:left="2px"
        android:right="2px"
        android:top="2px">
        <shape
            android:layout_width="wrap_content"
            android:layout_height="wrap_content">
            <corners android:radius="@dimen/btn_blue_radius" />
            <stroke
                android:width="2px"
                android:color="@color/btn_blue" />
        </shape>
    </item>
</layer-list>