Hello,
We have added below code to your custom CSS to change the color of the dark buttons and it works fine
.product-information .single_add_to_cart_button, button, .button, input[type=button], input[type=submit],
.wishlist_table .add_to_cart.button, .btn-black, .btn.btn-black,
.subscription-toggle, .btn.filled, .pagination-cubic li span.page-numbers.current{
background: green;
color:#fff;
}
.pagination-cubic li a:hover {
background: #3f9912;
}
Regards