Transparency on focused / unfocused windows

Question

Instead of using borders, I want to set alpha of focused and unfocused windows, for example, to 90% and 70%. This applies to all windows except those that meet some criteria like className = "Gimp". How can I implement this in my xmonad?

Thanks!

Answer 1

http://xmonad.org/xmonad-docs/xmonad-contrib/XMonad-Hooks-FadeInactive.html