litemdview/themes/gtkcssprovider.css

label {
  background-color: #222;
  color: #fff;
  padding-right: 5px;
}

entry,
entry:focus {
  background-image: none;
  background-color: #111;
  border-width: 0;
  border-style: inset;
  color: #fff;
  box-shadow: none;
  border-radius: 0;
}

* {
  border-color: transparent;
  border: none;
  box-shadow: none;
  border-radius: 0;
}