有透明的引导导航栏，希望导航栏保持透明，但菜单出现后，您单击汉堡包是彩色的

<nav class="navbar">
  <div class="navbar-brand">
    <a class="navbar-logo" href="#">Logo</a>
    <button class="navbar-toggler" type="button" onclick="toggleMenu()">
      <span class="navbar-toggler-icon"></span>
    </button>
  </div>
  <ul class="navbar-menu" id="navbarMenu">
    <li><a href="#">Home</a></li>
    <li><a href="#">About</a></li>
    <li><a href="#">Services</a></li>
    <li><a href="#">Contact</a></li>
  </ul>
</nav>

.navbar {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  background-color: transparent;
  z-index: 999;
}

.navbar-brand {
  display: flex;
  align-items: center;
  padding: 10px;
}

.navbar-logo {
  color: #fff;
  font-weight: bold;
  text-decoration: none;
}

.navbar-toggler {
  background-color: transparent;
  border: none;
  cursor: pointer;
}

.navbar-toggler-icon {
  display: inline-block;
  width: 20px;
  height: 20px;
  background-color: #fff;
}

.navbar-menu {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  width: 100%;
  background-color: #fff;
  padding: 10px;
}

.navbar-menu li {
  margin-bottom: 10px;
}

.navbar-menu li a {
  color: #000;
  text-decoration: none;
}

.show-menu {
  display: block;
}

function toggleMenu() {
  var navbarMenu = document.getElementById("navbarMenu");
  navbarMenu.classList.toggle("show-menu");
}