I think you should edit the anchor tag on bootstrap.css. Otherwise give customized style to the anchor tag with !important (to override the default style on bootstrap.css).
Example code
.nav {_x000D_
background-color: #000 !important;_x000D_
}_x000D_
_x000D_
.nav>li>a {_x000D_
background-color: #666 !important;_x000D_
color: #fff;_x000D_
}<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">_x000D_
_x000D_
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>_x000D_
_x000D_
_x000D_
<div role="tabpanel">_x000D_
_x000D_
<!-- Nav tabs -->_x000D_
<ul class="nav nav-tabs" role="tablist">_x000D_
<li role="presentation" class="active"><a href="#home" aria-controls="home" role="tab" data-toggle="tab">Home</a></li>_x000D_
<li role="presentation"><a href="#profile" aria-controls="profile" role="tab" data-toggle="tab">Profile</a></li>_x000D_
<li role="presentation"><a href="#messages" aria-controls="messages" role="tab" data-toggle="tab">Messages</a></li>_x000D_
<li role="presentation"><a href="#settings" aria-controls="settings" role="tab" data-toggle="tab">Settings</a></li>_x000D_
</ul>_x000D_
_x000D_
<!-- Tab panes -->_x000D_
<div class="tab-content">_x000D_
<div role="tabpanel" class="tab-pane active" id="home">...</div>_x000D_
<div role="tabpanel" class="tab-pane" id="profile">tab1</div>_x000D_
<div role="tabpanel" class="tab-pane" id="messages">tab2</div>_x000D_
<div role="tabpanel" class="tab-pane" id="settings">tab3</div>_x000D_
</div>_x000D_
_x000D_
</div>Fiddle: http://jsfiddle.net/zjjpocv6/2/