change color when i press my button

change color when i press my button

i whnt to make my button like this:
<?xml version="1.0" encoding="utf-8"?>
<!-- res/drawable/rounded_edittext.xml -->
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_focused="true"><shape android:padding="10dp"
android:shape="rectangle">
<solid android:color="#6699CC" />
<stroke android:height="10dp" android:width="2dp"
android:color="#ffffff" />
<corners android:radius="15dp" />
</shape></item>
<item><shape android:padding="10dp" android:shape="rectangle">
<solid android:color="#6699CC" />
<stroke android:height="10dp" android:width="2dp"
android:color="#780000" />
<corners android:radius="15dp" />
</shape></item>
</selector>
but i dont know how to change color when i press the button