<style> 
 .opening {
    width: 100px;
    height: 100px;
    background: white;
    -webkit-animation: changecolor 15s; /* Chrome, Safari, Opera */
    animation: changecolor 10s;
}

/* Chrome, Safari, Opera */
@-webkit-keyframes changecolor {
    from {background: #701028;}
    to {background: white;}
}

/* Standard syntax */
@keyframes changecolor {
    from {background: #b01030;}
    to {background: white;}
}
</style>