.wrap {
  display: flex;
  flex-direction: column;
}

pre {
  align-self: center;
  color: green;
  font-family: monospace;
  font-size: 1.8vw;
}

body {
  background-color: black;
}

@keyframes example {
  0%   {color: red}
  25%  {color: yellow}
  50%  {color: blue}
  100% {color: green}
}

.css {
  animation-name: example;
  animation-duration: 6s;
  animation-timing-function: ease;
  animation-iteration-count: infinite;
  animation-direction: alternate;
}