yellow color button in bootstrap code example

Example 1: bootstarp btn colors

<button type="button" class="btn btn-primary">Blue</button>
<button type="button" class="btn btn-secondary">Grey</button>
<button type="button" class="btn btn-success">Green</button>
<button type="button" class="btn btn-danger">Red</button>
<button type="button" class="btn btn-warning">Yellow</button>
<button type="button" class="btn btn-info">Ligth blue</button>
<button type="button" class="btn btn-light">White</button>
<button type="button" class="btn btn-dark">Black</button>

<button type="button" class="btn btn-link">White with blue text</button>

Example 2: bootstrap buttons Toggle states

Add data-toggle="button" to toggle a button’s active state. If you’re 
pre-toggling a button, you must manually add the .active class and
aria-pressed="true" to the <button>.

<button type="button" class="btn btn-primary" data-toggle="button" aria-pressed="false">
  Single toggle
</button>