<div class="center">
      <i class="fa fa-heart heart" aria-hidden="true"></i>
    </div>

body {
  height: 100vh;
  overflow: hidden;
}

.center {
  display: flex;
  justify-content: space-evenly;
  align-items: center;
  height: 100vh;
}

.heart {
  color: red;
  font-size: 50px;
  animation: heart-pulse 1s infinite ease-out;
}

@keyframes heart-pulse {
  0% {
    transform: scale(0);
    color:blue;
  }
  30% {
    transform: scale(2);
    color:green;
  }
  
   50% {
    transform: scale(1.2);
    color:red;
  }
  70% {
    transform: scale(0.65);
    color:green;
  }
  100% {
    transform: scale(0);
    color: red;
  }
}