Make Bootstrap Button Transparent

Question

How do I make my button transparent? I have been trying to use .btn-transparent but cant seem to get it to work. The button just keeps turning grey.

<p>
    <!-- Search Button -->
    <div class="container3">
        <div class="btn-group ">
            <button type="button" class="btn btn-primary-outline">SEARCH</button>
            <button type="button" class="btn btn-primary-outline">
                <span class="glyphicon glyphicon-menu-right"></span>
            </button>
        </div>
    </div>
</p>

Answer 1

make css to .btn-primary-outline

example like this : https://jsfiddle.net/472cxwg9/

Answer 2

Use

class="btn" and style="background-color:transparent" 

instead of

 class="btn btn-primary-outline"

result