Of course the counter-counter attack would be to randomly select some ratio of pixel locations based on the resolution of the image and toggle the red component on them.
I don't mean to sound like an asshole, but it seems to me that spending time working through the logistics of circumventing a bad piece of legislation that hasn't even passed yet to be a little like putting the cart before the horse.
This is still a political concern and the solution seems like it ought to be likewise. E.g. write your senator and congressperson, raise awareness (i recognize this is happening to some degree organically, since i just found out about it, but nonetheless), etc.
Have we become so cynical about the likelihood of being listened to that we assume bullshit laws will be passed and jump straight to figuring out how to get around them?
I'm not even thinking about the political side of all of this (and maybe I should). I just like to think about solving cool problems, such as how to detect these images if software that modifies pixels is used.