res/drawable/transparent_button_background.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@android:color/holo_blue_light" android:state_pressed="true"/>
    <item android:drawable="@android:color/holo_blue_light" android:state_pressed="true"/>
    <item android:drawable="@android:color/transparent" android:state_selected="false"/>
</selector>