How to change the color of button after click?

Question

I create button with background color but when i click on it, it's not show anything.
I need to show different color on button after click because user need to know button is
Click.
I don't understand how to do this?
Give me suggestion.
here is my button code.

<Button android:textSize="15px"
      android:id="@+id/button9" 
      android:gravity="center|bottom" 
      android:textColor="@color/myWhiteColor" 
      android:drawableTop="@drawable/math"
      android:text="@string/HomePage_Math" 
      android:background="@color/myMaroonColor" 
      android:layout_width="54dp" 
      android:layout_height="wrap_content" ></Button>

Answer 1

//XML file saved at res/drawable/button_bg.xml:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true"
          android:color="#ffff0000"/> <!-- pressed -->
    <item android:state_focused="true"
          android:color="#ff0000ff"/> <!-- focused -->
    <item android:color="#ff000000"/> <!-- default -->
</selector>

//This layout XML will apply the color list to a View:

<Button android:textSize="15px"
      android:id="@+id/button9" 
      android:gravity="center|bottom" 
      android:textColor="@color/myWhiteColor" 
      android:drawableTop="@drawable/math"
      android:text="@string/HomePage_Math" 
      android:background="@drawable/button_bg" 
      android:layout_width="54dp" 
      android:layout_height="wrap_content" ></Button>