Customised colours - Box-shadow example

index.html

<!-- This code example is not the same as GOV.UK Frontend, and is just for demonstration -->
<style>
  .round-button {
    font-size: 16px;
    border-radius: 50%;
    height: 6em;
    width: 6em;
  }

  .round-button:focus {
    outline: 3px solid transparent;
    outline-offset: 3px;
    box-shadow: 0 0 0 4px #ffbf47;
  }
</style>
<button class="round-button">
  Round button
</button>