<div class="r"></div>
<div class="g"></div>
<div class="b"></div>
div{
  display: inline-block;
  width: 100px;
  height: 100px;
}

.r{
  background-color: red;
}

.g{
    background-color: green;
}

.b{
    background-color: blue;
}

External CSS

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External JavaScript

This Pen doesn't use any external JavaScript resources.