[android help] Trying to set color to my text in android

I am trying to set color for my text in android. Every time i launch my application it shuts down. Here is what i have in color.xml file:

#006400
#FFE4C4

here is what i have in my MainActivity Class:

int textColor = getResources().getColor(R.color.app_text_color);

        TextView helloText = (TextView)findViewById(R.string.hello_world);

        helloText.setTextColor(textColor);

Here is the layout file:

    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

            android:id="@+id/hello_world"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world"
         />  

Log Car:

04-17 21:00:39.290: E/AndroidRuntime(9986):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1670)

.

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