bb-buttons.css

a.fl-button, 
a.fl-button:visited, 
.fl-builder-content a.fl-button, 
.fl-builder-content a.fl-button:visited {
  background: red;
  border: 1px solid red;
  border-radius: 20px;
}
a.fl-button *,
a.fl-button:visited *,
.fl-builder-content a.fl-button *,
.fl-builder-content a.fl-button:visited * {
  color: white;
}
a.fl-button:hover,
.fl-builder-content a.fl-button:hover {
  background: green;
  border: 1px solid green;
}
a.fl-button:hover *,
.fl-builder-content a.fl-button:hover * {
  color: black;
}