Bug 23459 add preference option to turn off variable guessing on method completion
request from Adam
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/JavaEditorPreferencePage.java
*/
	private void initializeViewerColors(ISourceViewer viewer) {
		
		IPreferenceStore store= fOverlayStore;
		if (store != null) {
			
			StyledText styledText= viewer.getTextWidget();
						
			
			Color color= store.getBoolean(AbstractTextEditor.PREFERENCE_COLOR_BACKGROUND_SYSTEM_DEFAULT)
				? null
				: createColor(store, AbstractTextEditor.PREFERENCE_COLOR_BACKGROUND, styledText.getDisplay());
			styledText.setBackground(color);
				
			if (fBackgroundColor != null)
				fBackgroundColor.dispose();
				
			fBackgroundColor= color;
		}
	}
	/**
	 * Creates a color from the information stored in the given preference store.
	 * Returns <code>null</code> if there is no such information available.
	 */
	private Color createColor(IPreferenceStore store, String key, Display display) {
	
		RGB rgb= null;		
		
		if (store.contains(key)) {