body {
  background-color: black;
  background-image: url("/images/stars2.gif");
}

.popup {
  border-color: purple;
  background-color: purple;
  margin: 1em;
}

.popup .content {
  background-color: silver;
}

.popup-button {
  background-color: silver;
  filter: saturate(50%);
}

.popup-button:nth-of-type(2) {
  background-color: green;
}

.popup-button:nth-of-type(3) {
  background-color: orange;
}

.popup-button:nth-of-type(4) {
  background-color: red;
}

.popup-button:hover {
  filter: saturate(150%);
}