.red-on-blue {
  background-color: #88f;
  color: #f88
}

.blue-on-red {
  background-color: #f88;
  color: #88f
}

.red-on-blue,
.blue-on-red {
  font-size: 2em;
  width: 300px;
  padding: 20px;
  margin: 10px
}
