How would you make a picture have the "Obama" color effect?

And if i do, would there be any chance that i would be sued? I want to use this effect to mimic an obama poster, because so many people know what it is, and seeing it around the school ( this is for an election) would catch an eye compared to the other bland looking papers. So if i have a picture, can someone point out how i can do this? Or can i send it to you to do it for me if its super duper complicated? :(