Change steam tray icon back to default

Change steam tray icon back to default

I have used this blog article http://www.webupd8.org/2013/02/get-ubuntu-mono-icons-for-steam-ubuntu.html to change the default tray steam icon to the one used in the article for Ubuntu-mono-dark. now I cant seem to change back to the default icon. the icon which is used for Ubuntu-mono-dark clashes with my new theme, where I cant seem to see the steam icon very well.