SOURCE

<div></div>

*, *::before, *::after {
  box-sizing: border-box;
}

html, body {
  height: 100%;
}

body {
  display: grid;
  align-items: center;
  justify-items: center;
  margin: 0;
  background-color: #000;
}

div {
  width: 300px;
  height: 300px;
  border-radius: 50%;
  box-shadow:
    0 0 20px #fff,
    -20px 0 80px #f0f,
    20px 0 80px #0ff,
    inset 0 0 50px #fff,
    inset 50px 0 80px #f0f,
    inset -50px 0 80px #0ff,
    inset 50px 0 300px #f0f,
    inset -50px 0 300px #0ff;
  animation: pulsate 6s linear infinite;
}

@keyframes pulsate {
  50% {
    box-shadow:
      0 0 20px #fff,
      20px 0 80px #f0f,
      -20px 0 80px #0ff,
      inset 0 0 50px #fff,
      inset -50px 0 80px #f0f,
      inset 50px 0 80px #0ff,
      inset -50px 0 300px #f0f,
      inset 50px 0 300px #0ff;
  }
}