Reply To: Button

Hello,

Please add this code to the Theme Settings > Custom CSS > Global:

.added_to_cart, 
.btn, 
.button, 
[type=button], 
[type=submit], button {
background:white!important;
color:blue!important;
border:2px solid blue!important;
}
.added_to_cart:hover, 
.btn:hover, 
.button:hover, 
[type=button]:hover, 
[type=submit]:hover, button {
background:blue!important;
color:white!important;
border:2px solid blue!important;
}

Set the styles as per your needs, there may be buttons which would requre the different styles, provide the page URL and how to change.

Best Regards