Change Theme Button Default Appearance

Hello-

I was wondering if there was a way to change the theme default button appearance? They are large, square, and raised and I’d like a more rectangular, flat, button appearance as I use through the rest of the site via customizable buttons in the builder. Please see the “sign-up” button in the footer and the “contact” button on the contact page (bostonrises.com). Please advise.

Thank you.