"submit" button in mailchimp naked form invisible

I've tried changing the color and size of the button in the CSS, but the changes aren't taking effect. I see the button and function of the button is working, but I can't see it. The test site I'm working on is: naturesgracetest.forestcreaturecreations.com See the screen shot here.. is there another style that's overriding it? Help much appreciated. Thank you! https://dl.dropboxusercontent.com/u/7367074/screenshot1.png