div#animado {
    margin: auto;
    margin-top: 20px;
    width: 200px;
    height: 200px;
    border: 1px outset black;
    box-shadow: 0 2px 4px black;
    background-color: #ffffff36;
    animation: moverYcambiar 4s infinite alternate;
}

@keyframes moverYcambiar {
    0% {
        background-color: #ffffff36;
        transform: translateX(0);
    }
    50% {
        background-color: #8080809c;
        transform: translateX(100px);
    }
    100% {
        background-color: #ffffff36;
        transform: translateX(0);
    }
}