Using Windows 7 Aero to dim or add a color hue to the whole desktop or a specific window

I would like to apply a light greenish or reddish hue to the entire desktop or select application windows using Windows开发者_如何学Go 7 Aero. Assuming this is this possible with Aero, is it possible with it so I could potentially port my application to XP?

You'd have a create a window that sits on top of the other windows you wish to dim/hue. This window would use the Aero API calls to enable transparency. For XP, you'd have to copy the contents of the screen to a bitmap, process the bitmap to make it look like you want, and create a window over the top of the other windows showing that bitmap. This technique would also work under Windows 7, but would not allow changes to any underlying windows to show through.