.your-block-class {
background: linear-gradient(45deg, #your-colors);
background-size: 400% 400%;
animation: gradientShift 8s ease infinite;
}
@keyframes gradientShift {
0% { background-position: 0% 50%; }
50% { background-position: 100% 50%; }
100% { background-position: 0% 50%; }
}