h1{
  animation: color-change 5s linear infinite;
  margin:20px;
  font-size:30px;
  font-weight: bold;
}

@keyframes color-change {
  0%,100%{
	color:#000000;
  }

  25%{
	color:#333333;
  }
  
  50%{
	color:#999999;
  }
  
  75%{
	color:#ffffff;
  }
}