vpnclient_ynh/sources/public/css/style.css

a.btn-danger span {
  color: #eee;
}

a.btn-danger:hover span {
  color: #fff;
}

a.not-allowed {
  cursor: not-allowed;
}

input.allowed {
  cursor: default;
}

a.btn-disabled, a.btn-disabled:hover, a.btn-disabled:active {
  background-color: #999;
  background-image: none;
  border-color: #888;
}

a.btn-disabled:hover span {
  color: #eee;
}