I was able to change the buttons using the following CSS selector
[/.w3eden .btn{
border: 0 !important;
border-radius: 25px !important;
background-color: #2DAAE1 !important;
color: #f5f5f5 !important;
line-height: 1 !important;
padding: 8.4px 14px 5.6px 14px !important;
outline: none !important;
-o-transition: background-color .3s ease-in-out !important;
-moz-transition: background-color .3s ease-in-out !important;
-webkit-transition: background-color .3s ease-in-out !important;
transition: background-color .3s ease-in-out !important;
}
.w3eden .btn:hover{
background-color: #121212 !important;
}
/]
Why do I need to use !important if I’m using the ‘Addditional CSS’ editor in the WP customize form?