div{
    width: 90%;
    height: 200px;
    margin: 0 auto 20px auto;
    border: 2px solid black;
    box-sizing: border-box;
}
.d1{
    background-color: orange;
    animation-name: couleur;
    animation-duration: 10s;
}
@keyframes couleur{
    from{
        background-color: orange;
    }
    25%{
        background-color: blue;
    }
    50%{
        background-color: purple;
    }
    75%{
        background-color: red;
    }
    to{
        background-color: orange;
    }
}