You could simply apply one of the bootstrap contextual background colors to the header row. In this case (blue background, white text): primary.
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">_x000D_
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap-theme.min.css" integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp" crossorigin="anonymous">_x000D_
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>_x000D_
_x000D_
<table class="table" >_x000D_
<tr class="bg-primary">_x000D_
<th>_x000D_
Firstname_x000D_
</th>_x000D_
<th>_x000D_
Surname_x000D_
</th>_x000D_
<th></th>_x000D_
</tr>_x000D_
<tr>_x000D_
<td>John</td>_x000D_
<td>Doe</td>_x000D_
</tr>_x000D_
<tr>_x000D_
<td>Jane</td>_x000D_
<td>Roe</td>_x000D_
</tr>_x000D_
</table>
_x000D_