CSS to make button green color

Hi there,

On our website eatrightpittsburgh.org/renewals there are a bunch of buttons that say Sign Up and Unsubscribe. You will need to be logged in to see them, and i can provide an account or support access should you need it. Anyways, we want the buttons to be the green color used throughout the website, can someone please suggest the CSS to do this? THanks very much!