javascript - 更改折叠菜单的背景颜色

Question

我的网站上有下拉菜单。这是代码

 <nav class="navbar navbar-custom navbar-fixed-top top-nav-collapse" role="navigation">
    <div class="container" style="height:80px;">
        <div class="navbar-header" style="">
            <button type="button" class="navbar-toggle glyphicon glyphicon-menu-hamburger" data-toggle="collapse" data-target=".navbar-main-collapse">
                <i class="fa fa-bars"></i>
            </button>
            <a class="navbar-brand page-scroll" href="#page-top">
                <i class="fa fa-play-circle"><img style="width:100px;height:50px;" src="/img/logo10.png"></i>

            </a>
        </div>

        <!-- Collect the nav links, forms, and other content for toggling -->
        <div class="collapse navbar-collapse navbar-right navbar-main-collapse" >
            <ul class="nav navbar-nav">
                <!-- Hidden li included to remove active class from about link when scrolled up past about section -->
                <li class="hidden">
                    <a href="#page-top"></a>
                </li>
                <li style="padding-top:10px;font-size:20px;" class="">
                    <a class="page-scroll" href="#about">О нас</a>
                </li>
                <li style="padding-top:10px;font-size:20px;" class="">
                    <a class="page-scroll" href="@Url.Action("Courses","Home")">Курсы</a>
                </li>
                <li style="padding-top:10px;font-size:20px;" class="">
                    <a class="page-scroll" href="@Url.Action("Development","Home")">Разработка</a>
                </li>
                <li style="padding-top:10px;font-size:20px;" class="active">
                    <a class="page-scroll" href="#contact">Контакты</a>
                </li>
                <li style="padding-top:10px;font-size:20px;" class="active">
                    <a class="page-scroll" href="@Url.Action("Index","Blog")">VR Блог</a>
                </li>
            </ul>
        </div>
        <!-- /.navbar-collapse -->
    </div>
    <!-- /.container -->
</nav>

现在它是透明的。我尝试将背景更改为红色。

这是bootstrap css的代码

   .navbar-nav > li > .dropdown-menu {
    margin-top: 0;
    border-top-left-radius: 0;
    border-top-right-radius: 0;
    background-color: red;
}

.navbar-fixed-bottom .navbar-nav > li > .dropdown-menu {
    margin-bottom: 0;
    border-top-left-radius: 4px;
    border-top-right-radius: 4px;
    border-bottom-right-radius: 0;
    border-bottom-left-radius: 0;
    background-color: red;
}

但它仍然保持透明。我不明白问题在哪里？

如何更改下拉菜单的背景颜色？

Answer 1

请在这里查看:https://jsbin.com/hekaxexeki/edit?html,css,output

.navbar-collapse.collapse.in{
  background-color:lightgreen;
}