Background

.test {
  width: 240px;
  height: 160px;
  margin: 40px auto;
  border: 1px solid black;
  animation: backgroundColorAnim 8s infinite;
}

@keyframes backgroundColorAnim {
  0% {
    background-color: crimson;
  }

  25% {
    background-color: #a5a5a5;
  }

  50% {
    background-color: rgba(10, 10, 235, 0.4);
  }

  75% {
    background-color: #00ff0033;
  }

  100% {
    background-color: crimson;
  }
}