a:link {
animation: rainbow 1s linear infinite;
}
@keyframes rainbow {
0% { color: hsl(0, 100%, 50%); }
50% { color: hsl(180, 100%, 50%); }
100% { color: hsl(360, 100%, 50%); }
}

.ui {
background: linear-gradient(to right, #f00 0%, #f80 14.28%, #dd0 28.56%, #0d0 42.85%, #0dd 57.14%, #00f 71.42%, #e0e 85.71%, #f00 100%) 0% center / 200% auto;
animation: rainbow-mohemohe 4s linear infinite;
}
@keyframes rainbow-mohemohe {
to {
background-position-x: 200%;
}
}