body {
    background-color: #000000;
}
.titel_body {
    width: 1200px;
    height: 400px;
    position: relative;
}
.titel_body:before, .titel_body:after {
    content: "";
    position: absolute;
    background: linear-gradient(30deg, red, orange, yellow, green, blue, indigo, violet);
    z-index: -1;
    width: calc(100% + 2px);
    height: calc(100% + 2px);
    top: -1px;
    left: -1px;
    background-size: 500%;
    animation: wandernderFarbverlauf 30s linear infinite;
}
.titel_body:after {
    filter: blur(40px);
}
@keyframes wandernderFarbverlauf {
    0%   { background-position: 0 0 }
    50%  { background-position: 500% 0 }
    100% { background-position: 0 0 }
}