Transparency on Focused/Unfocused windows

Question

Instead of using borders, I want to set the alpha of focused and unfocused windows to, say, 90% and 70%. This would apply to all windows except those matching some criterion 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