How to change the color of the dropdown menu button?

Question

Bootstrap

<li class="nav-item dropdown">
                        <a id="navbarDropdown" class="nav-link dropdown-toggle" href="#" data-toggle="dropdown">
                            {{ Auth::user()->name }} <span class="caret"></span>
                        </a>

                        <div class="dropdown-menu dropdown-menu-right">
                            <a class="dropdown-item" href="{{ route('logout') }}"
                               onclick="event.preventDefault();
                                             document.getElementById('logout-form').submit();">
                                {{ __('Выйти') }}
                            </a>
                        </div>
                    </li>

When you click on "Exit" it is highlighted in blue. And at the time of hovering in gray. How to make green when you click and when you move the mouse?