<div class="container">
    <div class="filter-mix"></div>
</div> 

.filter-mix {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 300px;
    height: 200px;
    filter: contrast(20);
    background: #fff;
}

.filter-mix::before {
    content: "";
    position: absolute;
    width: 120px;
    height: 120px;
    border-radius: 50%;
    background: #333;
    top: 40px;
    left: 40px;
    z-index: 2;
    filter: blur(6px);
    box-sizing: border-box;
    animation: filterBallMove 4s ease-out infinite;
}

.filter-mix::after {
    content: "";
    position: absolute;
    width: 80px;
    height: 80px;
    border-radius: 50%;
    background: #3F51B5;
    top: 60px;
    right: 40px;
    z-index: 2;
    filter: blur(6px);
    animation: filterBallMove2 4s ease-out infinite;
}

@keyframes filterBallMove {
    50% {
        left: 140px;
    }
}

@keyframes filterBallMove2 {
    50% {
        right: 140px;
    }
}