Just turn up the brightness. Way up.
Serious answer: I highly doubt if this is even possible. You don't say what version of Windows you use. If it's XP or earlier, the desktop/etc is rendered using GDI (possibly sitting on top of DirectDraw) which doesn't support this kind of effect.
For Vista or later (assuming Aero is running - if not you're SoL) the desktop is rendered using D3D9 and a pixel shader. A search on Google (novel concept, that!) for "windows desktop custom shaders" indicates that there is no supported way to use your own shaders here.
No doubt some "power user" (translation: someone with just about enough knowledge for it to be a dangerous thing) will cook up a solution sometime involving True Evil like hacking the D3D DLLs (thus breaking everything any time D3D gets updated), intercepting undocumented window messages, and modifying undocumented structures. And when it does keel over and die people will blame Windows for being buggy rather than point the finger in the right direction.
