ul {
    padding-left: 0;
    overflow: hidden;
    white-space: nowrap;
    width: 300px;
}

li {
    display: inline-block;
    height: 50px;
    width:  50px;
}

li:nth-child(odd) {
    background-color: red;
}

li:nth-child(even) {
    background-color: blue;
}

@media (max-width: 640px) {
    button {
        display: none;
    }

    ul {
        overflow: auto;
    }
}