<!DOCTYPE html>
<html>
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<style>
 .dropdown > .dropdown-toggle.btn-default:focus{background:gray} .open > .dropdown-toggle.btn-default[aria-expanded=true] {background:red}

  
  
  </style>
  
  
  </head>
<body>

<div class="container">
  <h2>Dropdowns</h2>
  <p>The .dropdown class is used to indicate a dropdown menu.</p>
  <p>Use the .dropdown-menu class to actually build the dropdown menu.</p>
  <p>To open the dropdown menu, use a button or a link with a class of .dropdown-toggle and data-toggle="dropdown".</p>                                          
  <div class="dropdown">
    <button class="btn btn-default btncolor1 dropdown-toggle" type="button" data-toggle="dropdown">Dropdown Example
    <span class="caret"></span></button>
    <ul class="dropdown-menu dropdwn1">
      <li><a href="#">HTML</a></li>
      <li><a href="#">CSS</a></li>
      <li><a href="#">JavaScript</a></li>
    </ul>
  </div>
</div>

</body>
</html>

.btncolor1 {
    	background-color:darkred;
        color:yellow;
    }
    .btncolor1:hover,
    .btncolor1:focus{
    	background-color:red;
        color:yellow;
    }
     .open {
    	background-color:pink;
    }
     .dropdwn1 {
    	background-color:lightgreen;
    }
    .dropdwn1 > li a{
    	background-color:lightgreen;
        color:green;
    }
    .dropdwn1 > li a:hover{
    	background-color:green;
        color:lightgreen;
    }
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External JavaScript

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