<div class="block blue"></div>
<div class="block yellow"></div>
<div class="block green"></div>
.block{
  display:block;
  width: 50px;
  height: 50px;
}

.yellow{
    background-color: yellow;
}
.green{
    background-color: green;
}

.blue{
     background-color: blue;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.