Template:Animatedrainbowtext/styles.css

@keyframes rainbow{
   0%{color: red;}
   14%{color: orange;}
   28%{color: yellow;}
   42%{color: green;}
   56%{color: cyan;}
   70%{color: blue;}
   84%{color: violet;}
   100%{color: red;}
}

.rainbow {
 animation: 5s rainbow infinite;
}

p {
  margin: 0 !important;
}