I want to display the below warning message(message bar) on saving a component in Tridion 2013.
xCustomMessage = "There is a localized version of this component."; Logger.WriteInfo(xCustomMessage);
I am pretty sure that you can only show message bar errors directly from your event system code by raising exceptions from GUI triggered events (like saving a component) - however this would be an error rather than a warning, and would also prevent the component being saved.
In order to have more control over messages in the message bar, you have to undertake a more complicated approach, which will involve a GUI extension to poll for messages which you send from a server - as outlined in this article. The advantage of this approach is that you can send any kind of messages from anywhere, but it maybe a bit of a sledgehammer approach for your rather simple problem.