transparent shader that changes color to objects behind it.

I’m very new to shaders, but I think is the way to go, I’ve been looking a way to change UI Text to a specific color, I found a transparent shader that inverts the color when ever you put it on top of images or UI Elements:
Unfortunately this won’t work, since I need the output color to a specific one. Any help on how to do this with shaders or any other ideas are greatly appreciate it.

Yes, I want it too!