Add .dropdown-menu-dark (#30171)

* Add .dropdown-menu-dark

* Match background color to navbar dark

* Update docs to include a navbar example

* Update dropdowns.md

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

scss/_dropdown.scss

@@ -193,3 +193,44 @@
   padding: $dropdown-item-padding-y $dropdown-item-padding-x;
   color: $dropdown-link-color;
 }
+
+// Dark dropdowns
+.dropdown-menu-dark {
+  color: $dropdown-dark-color;
+  background-color: $dropdown-dark-bg;
+  border-color: $dropdown-dark-border-color;
+  @include box-shadow($dropdown-dark-box-shadow);
+
+  .dropdown-item {
+    color: $dropdown-dark-link-color;
+
+    &:hover,
+    &:focus {
+      color: $dropdown-dark-link-hover-color;
+      @include gradient-bg($dropdown-dark-link-hover-bg);
+    }
+
+    &.active,
+    &:active {
+      color: $dropdown-dark-link-active-color;
+      @include gradient-bg($dropdown-dark-link-active-bg);
+    }
+
+    &.disabled,
+    &:disabled {
+      color: $dropdown-dark-link-disabled-color;
+    }
+  }
+
+  .dropdown-divider {
+    border-color: $dropdown-dark-divider-bg;
+  }
+
+  .dropdown-item-text {
+    color: $dropdown-dark-link-color;
+  }
+
+  .dropdown-header {
+    color: $dropdown-dark-header-color;
+  }
+}

scss/_variables.scss

@@ -950,6 +950,19 @@ $dropdown-item-padding-x:           $spacer !default;
 $dropdown-header-color:             $gray-600 !default;
 $dropdown-header-padding:           $dropdown-padding-y $dropdown-item-padding-x !default;
 
+$dropdown-dark-color:               $gray-300 !default;
+$dropdown-dark-bg:                  $gray-800 !default;
+$dropdown-dark-border-color:        $dropdown-border-color !default;
+$dropdown-dark-divider-bg:          $dropdown-divider-bg !default;
+$dropdown-dark-box-shadow:          null !default;
+$dropdown-dark-link-color:          $dropdown-dark-color !default;
+$dropdown-dark-link-hover-color:    $white !default;
+$dropdown-dark-link-hover-bg:       rgba($white, .15) !default;
+$dropdown-dark-link-active-color:   $dropdown-link-active-color !default;
+$dropdown-dark-link-active-bg:      $dropdown-link-active-bg !default;
+$dropdown-dark-link-disabled-color: $gray-500 !default;
+$dropdown-dark-header-color:        $gray-500 !default;
+
 
 // Pagination
 

site/content/docs/5.0/components/dropdowns.md

@@ -347,6 +347,52 @@ Button dropdowns work with buttons of all sizes, including default and split dro
 </div>
 {{< /highlight >}}
 
+## Dark dropdowns
+
+Opt into darker dropdowns to match a dark navbar or custom style by adding `.dropdown-menu-dark` onto an existing `.dropdown-menu`. No changes are required to the dropdown items.
+
+{{< example >}}
+<div class="dropdown">
+  <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenuButton2" data-toggle="dropdown" aria-expanded="false">
+    Dropdown button
+  </button>
+  <ul class="dropdown-menu dropdown-menu-dark" aria-labelledby="dropdownMenuButton2">
+    <li><a class="dropdown-item active" href="#">Action</a></li>
+    <li><a class="dropdown-item" href="#">Another action</a></li>
+    <li><a class="dropdown-item" href="#">Something else here</a></li>
+    <li><hr class="dropdown-divider"></li>
+    <li><a class="dropdown-item" href="#">Separated link</a></li>
+  </ul>
+</div>
+{{< /example >}}
+
+And putting it to use in a navbar:
+
+{{< example >}}
+<nav class="navbar navbar-expand-lg navbar-dark bg-dark">
+  <div class="container-fluid">
+    <a class="navbar-brand" href="#">Navbar</a>
+    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNavDarkDropdown" aria-controls="navbarNavDarkDropdown" aria-expanded="false" aria-label="Toggle navigation">
+      <span class="navbar-toggler-icon"></span>
+    </button>
+    <div class="collapse navbar-collapse" id="navbarNavDarkDropdown">
+      <ul class="navbar-nav">
+        <li class="nav-item dropdown">
+          <a class="nav-link dropdown-toggle" href="#" id="navbarDarkDropdownMenuLink" role="button" data-toggle="dropdown" aria-expanded="false">
+            Dropdown
+          </a>
+          <ul class="dropdown-menu dropdown-menu-dark" aria-labelledby="navbarDarkDropdownMenuLink">
+            <li><a class="dropdown-item" href="#">Action</a></li>
+            <li><a class="dropdown-item" href="#">Another action</a></li>
+            <li><a class="dropdown-item" href="#">Something else here</a></li>
+          </ul>
+        </li>
+      </ul>
+    </div>
+  </div>
+</nav>
+{{< /example >}}
+
 ## Directions
 
 ### Dropup