Android style specify button color

Question

I am trying to apply a button text color by default in styles.xml

<resources xmlns:android="http://schemas.android.com/apk/res/android">
<style name="AppTheme">
   <item name="android:windowFullscreen">true</item>
   <item name="android:windowBackground">@color/black</item>
   <item name="android:textColor">@color/green</item>
</style> 

How do I make the style change button color, and apply throughout the entire application? My mainfest includes:

    <application
    android:icon="@drawable/ic_launcher"
    android:label="Hack the World"
    android:theme="@style/AppTheme">

This changes all text (such as a TextView), but does not change the text in a button. If I use the ColorThemes style from above and place it in the xml for the button like this:

    <Button
    android:id="@+id/button3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:onClick="loadSavedgame"
    android:text="Load Saved Game" 
    android:textColor="@color/green" />"

Then it works perfectly. Why doesn't this apply universally because of the style? All different versions of styles.xml have the same code.

Solution

I eventually discovered that a button is, in fact, a 9-patch image that is located at @android:drawable/btn_default in order to change the background you must modify this image. In order to change button text color I had to set a button widget style and import it into my app theme like so:

<resources xmlns:android="http://schemas.android.com/apk/res/android">
<style name="AppTheme" parent="android:Theme.Holo.Light.DarkActionBar" >
   <item name="android:windowFullscreen">true</item>
   <item name="android:windowBackground">@color/black</item>
   <item name="android:textColor">@color/green</item>
   <item name="android:buttonStyle">@style/ButtonText</item>
</style> 

    <style name="ButtonText" parent="@android:style/Widget.Button">
   <item name="android:textColor">@color/green</item>
   <item name="android:background">@android:drawable/btn_default</item><!-- only way to change this is to change the src image -->
   <item name="android:layout_width">80.0px</item>
   <item name="android:layout_height">40.0px</item> 
</style> 
</resources>