Hi jaspud – I am not the plugin author, but I spotted your message.
Below is the custom CSS that I’ve used on my site – something similar will probably work for you too. Add to the bottom of your STYLES.CSS file in the usual way.
The first part is the normal button, followed by the colors for HOVER and ACTIVE (clicked) –
.scbb-button-blue {
background-color: #80ABC4 !important;
color: #222222 !important;
border: 1px solid #ffffff !important;}
.scbb-button-blue:hover {
background-color: #005789 !important;
color: #ffffff !important;
border: 1px solid #ffffff !important;}
.scbb-button-blue:active {
background-color: #005789 !important;
color: #cccccc!important;
border: 1px solid #ffffff !important;}