background: linear-gradient(270deg, #ff0000, #ff8800, #ffff00, #00ff00, #0000ff, #8888ff, #8800ff);
background-size: 1400% 1400%;
-webkit-animation: AnimationName 30s ease infinite;
-moz-animation: AnimationName 30s ease infinite;
-o-animation: AnimationName 30s ease infinite;
animation: AnimationName 30s ease infinite;
@-webkit-keyframes AnimationName {
    0%{background-position:0% 50%}
    50%{background-position:100% 50%}
    100%{background-position:0% 50%}
}
@-moz-keyframes AnimationName {
    0%{background-position:0% 50%}
    50%{background-position:100% 50%}
    100%{background-position:0% 50%}
}
@-o-keyframes AnimationName {
    0%{background-position:0% 50%}
    50%{background-position:100% 50%}
    100%{background-position:0% 50%}
}
@keyframes AnimationName {
    0%{background-position:0% 50%}
    50%{background-position:100% 50%}
    100%{background-position:0% 50%}
}