Woocommerce button style

I am using woocommerce on my site(https://masterscoffeeandwater.com/bottled-water/) and I want to style button “add to cart” on my site ,currently it is appearing as text link that is very boring ..

I am using below CSS but it’s not working

.single_add_to_cart_button:hover {
background: green !important;
}
.single_add_to_cart_button {
background: red !important;
}

any help would be appreciated

I am stuck here