Hello, @IP,
Unfortunately, there is no option in the Theme Settings to edit those buttons directly, but you can only turn ON and OFF the Sticky Add to Cart from Theme Settings, If you want to change the color of the Add to Cart button, you have to use the Custom CSS for it.
body .etheme-sticky-cart button.add_to_cart_button.ajax_add_to_cart.single_add_to_cart_button {
background-color: red !important;
}
Regards 8Themes Team.