I am struggling with this as well. I have tried entering CSS to change the button color but the plugin is overriding and keeping it as that bland shade of green. Really need to be able to control this and have asked in a numerous forums with no help and/or no solution.
How to Get Support
After you register and login to the site, you may post all plugin support questions in the Support Forum.
If you need to provide private info, please create a ticket and then reply to it using Set as private reply option.