<ul>
  <li>1</li>
  <li>2</li>
  <li>3</li>
  <li>4</li>
</ul>

body {
  font: 16px "Helvetica Neue", sans-serif;
  color: #fff;
  padding-top: 50px;
}

ul {
  list-style: none;
  display: flex;
  margin: 0;
  padding: 0;
}

li {
  flex: 1;
  padding: 15px;
  text-align: center;
}

li:nth-child(1) {
  order: 4;
  background: green;
}

li:nth-child(2) {
  order: 1;
  background: red;
}

li:nth-child(3) {
  order: 2;
  background: steelblue;
}

li:nth-child(4) {
  order: 3;
  background: orange;
}