Submit Button Color

You would target the button that has a class of .button within the .gform_footer div by adding CSS to your themes stylesheet that targets these elements. For example, you would add CSS similar to the snippet below to your themes stylesheet:

.gform_footer .button {background-color: #XXXXXX; color: #XXXXXX;}

Of course changing out the hex values for whatever you want.

There shouldn't be anything else you need to do. If you can post a link to your form I can look at it and see how you added the CSS to see why it isn't working.

Your theme already has Gravity Forms styles added to it. So when you try to override the Gravity Forms styles in your Theme's Style.css file it is getting overridden by other styles your theme calls from here:

http://www.brettsebens.com/wp-content/themes/organic_portfolio_white/includes/organic_gforms.css?ver=3.0

That is where you would need to make your style changes. Edit that file and find the .button class and you'll see it is being set in that CSS file which is called AFTER the Style.css and therefore is overriding it.

So make your changes in the file referenced above.