Hello,
To get what you want, please insert the following codes into Customizing->General->Additional CSS:
.show_details_button{
display: none!important;
}
a.button.product_type_simple.add_to_cart_button.ajax_add_to_cart,
a.button.product_type_variable.add_to_cart_button,
a.button.add_to_cart_button.more_info_button.out_stock_button{
font-family: Raleway,Helvetica,Arial,sans-serif;
font-weight: 700!important;
color: white!important;
}
.custom_cart_button.single_button.clearfix,
.custom_cart_button.clearfix{
background-color:#a2c605!important;
}
Change the values per your needs.
Regards