Bug 13507 LinkedPositionUI has a reference to SWT.COLOR_RED
LinkedPositionUI(ITextViewer, LinkedPositionManager) - org.eclipse.jdt.internal.ui.text.link.LinkedPositionUI has a reference to SWT.COLOR_RED which will be unreadble if the user sets their background colour to Red. We will be adding a getErrorText colour to JFaceColours in build >20020411. You may want to use that.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/link/LinkedPositionUI.java
/*
	 * @see ModifyListener#modifyText(ModifyEvent)
	 */	 
	public void modifyText(ModifyEvent e) {
		
		redrawRegion();
		updateCaret();
	}
	private static void openErrorDialog(Shell shell, Exception e) {
		MessageDialog.openError(shell, LinkedPositionMessages.getString("LinkedPositionUI.error.title"), e.getMessage()); 
	}
	/*
	 * @see ITextInputListener#inputDocumentAboutToBeChanged(IDocument, IDocument)
	 */
	public void inputDocumentAboutToBeChanged(IDocument oldInput, IDocument newInput) {
		
		int flags= UNINSTALL | COMMIT | (oldInput.equals(newInput) ? 0 : DOCUMENT_CHANGED);
		leave(flags);
	}
	/*
	 * @see ITextInputListener#inputDocumentChanged(IDocument, IDocument)
	 */
	public void inputDocumentChanged(IDocument oldInput, IDocument newInput) {
	}
	private static boolean includes(IRegion region, Position position) {
		return
			position.getOffset() >= region.getOffset() &&
			position.getOffset() + position.getLength() <= region.getOffset() + region.getLength();
	}
}