Jak zrobić kwadraty kolorów w kątowych

<div><div class='box red'></div>= Super Fast Trains</div>
<br>
<div><div class='box green'></div>= Mail/Express Trains</div>
<br>
<div><div class='box blue'></div>= Local/ Passenger Trains</div>


// CSS

.box {
  float: left;
  height: 20px;
  width: 20px;
  margin-bottom: 15px;
  border: 1px solid black;
  clear: both;
}

.red {
  background-color: red;
}

.green {
  background-color: green;
}

.blue {
  background-color: blue;
}
Cautious Cicada