You are referring to the Touchwiz email app and not Gmail correct? I know my gmail app right now is black text on a white background. I can't remember what it looked like when I was stock. Anyway, you could always have your other email accounts piped through gmail and then it will all get pushed into the same inbox and have the black text/white background of the gmail app. That is a win/win!
Other than that you would have to just get a 3rd party email app.