.rainbow {
  background-color: blueviolet;
}

.rainbow {
  background: linear-gradient(
    124deg,
    #ff2400,
    #e81d1d,
    #e8b71d,
    #e3e81d,
    #1de840,
    #1ddde8,
    #2b1de8,
    #dd00f3,
    #dd00f3
  );
  background-size: 1800% 1800%;

  -webkit-animation: rainbow 18s ease infinite;
  -z-animation: rainbow 18s ease infinite;
  -o-animation: rainbow 18s ease infinite;
  animation: rainbow 18s ease infinite;
}

@-webkit-keyframes rainbow {
  0% {
    background-position: 0% 82%;
  }
  50% {
    background-position: 100% 19%;
  }
  100% {
    background-position: 0% 82%;
  }
}
@-moz-keyframes rainbow {
  0% {
    background-position: 0% 82%;
  }
  50% {
    background-position: 100% 19%;
  }
  100% {
    background-position: 0% 82%;
  }
}
@-o-keyframes rainbow {
  0% {
    background-position: 0% 82%;
  }
  50% {
    background-position: 100% 19%;
  }
  100% {
    background-position: 0% 82%;
  }
}
@keyframes rainbow {
  0% {
    background-position: 0% 82%;
  }
  50% {
    background-position: 100% 19%;
  }
  100% {
    background-position: 0% 82%;
  }
}