First, install the packages "compizconfig-settings-manager" and "compiz-plugins-extra". Use this command:
Code:
sudo apt-get install compiz-plugins-extra compizconfig-settings-manager
Then open the program ccsm (CompizConfig Settings Manager). It contains a plugin called "Opacity, Brightness and Saturation" which controls the opacity, brightness and saturation of windows.
However, after experimenting for a while, it appears that this plugin cannot be applied to the Unity launcher and panel, since probably it's composited differently than the rest of the desktop (this problem also affects the zoom plugin). It means that this plugin can make any part of your screen (desktop background, windows, etc. etc.) black and white BUT the launcher and panel. So, unless someone knows something that I don't, what you're asking for is impossible. If you are still curious as to how to make a window black and white, then: In ccsm, enable the plugin "Opacity, Brightness and Saturation". Wait a while for Compiz to sort itself out, then open it, go to the "Saturation" tab. On the
second "Increase Saturation" entry, click it, choose "Ctrl", "Alt", and "Button4". Same for the
second "Decrease Saturation" entry, but "Button5" instead of "Button4".
Now, hover your mouse on any windows, hold Ctrl + Alt and scroll down with the middle mouse button to make your window go black and white! To make it colorful again, Ctrl + Alt + Scroll up. This might be enough to amaze your friend.
http://ubuntuforums.org/showthread.php?t=2143868