diff --git a/addons/rose/addon/components/rose/dropdown/index.hbs b/addons/rose/addon/components/rose/dropdown/index.hbs
index 457f4a5a3..587b8c369 100644
--- a/addons/rose/addon/components/rose/dropdown/index.hbs
+++ b/addons/rose/addon/components/rose/dropdown/index.hbs
@@ -28,6 +28,7 @@
       button=(component "rose/dropdown/button" style=this.style)
       item=(component "rose/anonymous" class="rose-dropdown-item")
       separator=(component "rose/anonymous" tagName="hr" class="rose-dropdown-separator")
+      section=(component "rose/dropdown/section" style=this.style)
     )}}
   </div>
 
diff --git a/addons/rose/addon/components/rose/dropdown/index.stories.mdx b/addons/rose/addon/components/rose/dropdown/index.stories.mdx
index 718f5fccd..a6b7a1b52 100644
--- a/addons/rose/addon/components/rose/dropdown/index.stories.mdx
+++ b/addons/rose/addon/components/rose/dropdown/index.stories.mdx
@@ -9,13 +9,17 @@ import { boolean } from '@storybook/addon-knobs';
 A simple dropdown component with support for links and buttons.
 
 <Preview>
-  <Story name="Basic Dropdown" height="5rem">{{
+  <Story name="Basic Dropdown" height="7rem">{{
     template: hbs`
       <Rose::Dropdown @text="Choose One&hellip;" @icon="user-organization" @showCaret={{showCaret}} as |dropdown|>
         <dropdown.link @route="index">Menu item</dropdown.link>
         <dropdown.link @route="about">Menu item</dropdown.link>
         <dropdown.separator />
         <dropdown.button>Button menu item</dropdown.button>
+        <dropdown.separator />
+        <dropdown.section @title="Dropdown Section Title">
+          <dropdown.link @route="index">Menu item</dropdown.link>
+        </dropdown.section>
       </Rose::Dropdown>
     `,
     context: {
@@ -65,6 +69,10 @@ A simple dropdown component with support for links and buttons.
     <dropdown.link @route="index">Menu item</dropdown.link>
     <dropdown.link @route="about">Menu item</dropdown.link>
     <dropdown.button>Button menu item</dropdown.button>
+    <dropdown.separator />
+    <dropdown.section @title="Dropdown Section Title">
+      <dropdown.link @route="index">Menu item</dropdown.link>
+    </dropdown.section>
   </Rose::Dropdown>
 ```
 
diff --git a/addons/rose/addon/components/rose/dropdown/section/index.hbs b/addons/rose/addon/components/rose/dropdown/section/index.hbs
new file mode 100644
index 000000000..10476dd8c
--- /dev/null
+++ b/addons/rose/addon/components/rose/dropdown/section/index.hbs
@@ -0,0 +1,12 @@
+<section class="rose-dropdown-section" aria-labelledby={{concat "dropdown-section-title-" this.id}}>
+  {{#if @title}}
+    <h2
+      id={{concat "dropdown-section-title-" this.id}}
+      class="rose-dropdown-section-title"
+    >
+      {{@title}}
+    </h2>
+  {{/if}}
+
+  {{yield}}
+</section>
diff --git a/addons/rose/addon/components/rose/dropdown/section/index.js b/addons/rose/addon/components/rose/dropdown/section/index.js
new file mode 100644
index 000000000..eb2727185
--- /dev/null
+++ b/addons/rose/addon/components/rose/dropdown/section/index.js
@@ -0,0 +1,14 @@
+import Component from '@glimmer/component';
+import { generateComponentID } from '../../../../utilities/component-auto-id';
+import { action } from '@ember/object';
+
+export default class RoseDialogComponent extends Component {
+
+  // =attributes
+
+  /**
+   * @type {string}
+   */
+  id = generateComponentID();
+
+}
diff --git a/addons/rose/addon/components/rose/form/radio/group/index.hbs b/addons/rose/addon/components/rose/form/radio/group/index.hbs
index 76cfea93b..fc34bd1cc 100644
--- a/addons/rose/addon/components/rose/form/radio/group/index.hbs
+++ b/addons/rose/addon/components/rose/form/radio/group/index.hbs
@@ -1,3 +1,3 @@
 {{yield (hash
-  radio=(component 'rose/form/radio/radio' name=@name selectedValue=@selectedValue disabled=@disabled)
+  radio=(component 'rose/form/radio/radio' name=@name selectedValue=@selectedValue disabled=@disabled changed=@changed)
 )}}
diff --git a/addons/rose/addon/components/rose/form/radio/group/index.stories.mdx b/addons/rose/addon/components/rose/form/radio/group/index.stories.mdx
index e6c750487..bafffaaa4 100644
--- a/addons/rose/addon/components/rose/form/radio/group/index.stories.mdx
+++ b/addons/rose/addon/components/rose/form/radio/group/index.stories.mdx
@@ -1,5 +1,6 @@
 import { Meta, Story, Preview } from '@storybook/addon-docs/blocks';
 import { hbs } from 'ember-cli-htmlbars';
+import { action } from '@storybook/addon-actions';
 import { text, boolean, select } from '@storybook/addon-knobs';
 
 <Meta title="Rose|Form/Radio/Group" component="Form/Radio/Group" />
@@ -13,6 +14,7 @@ Renders a form radiofield group.
   @disabled={{false}}
   @name={{name}}
   @selectedValue="disagree"
+  @changed={{fn}}
   as |radioGroup|
 >
   <radioGroup.radio
@@ -36,6 +38,7 @@ Renders a form radiofield group.
       @disabled={{disabled}}
       @name={{name}}
       @selectedValue={{selectedValue}}
+      @changed={{changed}}
       as |radioGroup|
     >
       <radioGroup.radio
@@ -73,6 +76,7 @@ Renders a form radiofield group.
     secondFieldValue: text('second value', 'maybe'),
     thirdFieldLabel: text('third label', 'Disagree'),
     thirdFieldValue: text('third value', 'disagree'),
+    changed: action('changed')
   }
   }}</Story>
 </Preview>
diff --git a/addons/rose/addon/components/rose/form/radio/radio/index.hbs b/addons/rose/addon/components/rose/form/radio/radio/index.hbs
index 62d571197..dcd450a8b 100644
--- a/addons/rose/addon/components/rose/form/radio/radio/index.hbs
+++ b/addons/rose/addon/components/rose/form/radio/radio/index.hbs
@@ -9,7 +9,8 @@
     @name={{@name}}
     @value={{@value}}
     @groupValue={{@selectedValue}}
-    @disabled={{@disabled}}/>
+    @disabled={{@disabled}}
+    @changed={{@changed}} />
 
   <label class="rose-form-radio-label" for={{this.id}}>
 
diff --git a/addons/rose/addon/components/rose/form/radio/radio/index.stories.mdx b/addons/rose/addon/components/rose/form/radio/radio/index.stories.mdx
index 425ea6e53..633a5c082 100644
--- a/addons/rose/addon/components/rose/form/radio/radio/index.stories.mdx
+++ b/addons/rose/addon/components/rose/form/radio/radio/index.stories.mdx
@@ -15,6 +15,7 @@ Renders a form radiofield.
   @value="yes-agree"
   @selectedValue="yes-agree"
   @disabled={{false}}
+  @changed={{fn}}
   />
 ```
 
diff --git a/addons/rose/addon/styles/rose/components/card/_link.scss b/addons/rose/addon/styles/rose/components/card/_link.scss
index 605b274cb..8c102c151 100644
--- a/addons/rose/addon/styles/rose/components/card/_link.scss
+++ b/addons/rose/addon/styles/rose/components/card/_link.scss
@@ -6,6 +6,24 @@
 $xxxs: sizing.rems(xxxs); // 2
 
 .rose-card-link {
+
+  --background-color-light: transparent;
+  --background-color-dark: var(--ui-gray-subtler-6);
+
+  --background-color: var(--background-color-light);
+  
+  .ember-application.rose-theme-light & {
+    --background-color: var(--background-color-light);
+  }
+
+  @media (prefers-color-scheme: dark) {
+    --background-color: var(--background-color-dark);
+  }
+
+  .ember-application.rose-theme-dark & {
+    --background-color: var(--background-color-dark);
+  }
+
   @include type.type(s);
   border: sizing.rems(xxxxs) solid var(--ui-gray-subtler-2);
   border-radius: sizing.rems(xxxs);
@@ -15,10 +33,7 @@ $xxxs: sizing.rems(xxxs); // 2
   margin: 0 sizing.rems(m) sizing.rems(m) 0;
   box-shadow: 0 $xxxs $xxxs rgba(var(--stark-components), var(--opacity-4)),
     0 $xxxs $xxxs rgba(var(--stark-components), var(--opacity-4));
-
-  @media (prefers-color-scheme: dark) {
-    background-color: var(--ui-gray-subtler-6);
-  }
+  background-color: var(--background-color);
 
   a {
     text-decoration: none;
diff --git a/addons/rose/addon/styles/rose/components/dropdown/_dropdown.scss b/addons/rose/addon/styles/rose/components/dropdown/_dropdown.scss
index 0c0069b00..4b75b3ad5 100644
--- a/addons/rose/addon/styles/rose/components/dropdown/_dropdown.scss
+++ b/addons/rose/addon/styles/rose/components/dropdown/_dropdown.scss
@@ -3,10 +3,27 @@
 
 $xs: sizing.rems(xs); // 8
 $xxs: sizing.rems(xxs); // 4
-$chevron: "data:image/svg+xml;utf-8,<svg viewBox='0 0 24 24' fill='%231b1f26' xmlns='http://www.w3.org/2000/svg'><path fill-rule='evenodd' clip-rule='evenodd' d='M16.59 8.59L12 13.17 7.41 8.59 6 10l6 6 6-6-1.41-1.41z'></path></svg>";
-$chevronWhite: "data:image/svg+xml;utf-8,<svg viewBox='0 0 24 24' fill='%23ffffff' xmlns='http://www.w3.org/2000/svg'><path fill-rule='evenodd' clip-rule='evenodd' d='M16.59 8.59L12 13.17 7.41 8.59 6 10l6 6 6-6-1.41-1.41z'></path></svg>";
+$chevron: url("data:image/svg+xml;utf-8,<svg viewBox='0 0 24 24' fill='%231b1f26' xmlns='http://www.w3.org/2000/svg'><path fill-rule='evenodd' clip-rule='evenodd' d='M16.59 8.59L12 13.17 7.41 8.59 6 10l6 6 6-6-1.41-1.41z'></path></svg>");
+$chevronWhite: url("data:image/svg+xml;utf-8,<svg viewBox='0 0 24 24' fill='%23ffffff' xmlns='http://www.w3.org/2000/svg'><path fill-rule='evenodd' clip-rule='evenodd' d='M16.59 8.59L12 13.17 7.41 8.59 6 10l6 6 6-6-1.41-1.41z'></path></svg>");
 
 .rose-dropdown {
+  --background-image-light: #{$chevron};
+  --background-image-dark: #{$chevronWhite};
+
+  --background-image: var(--background-image-light);
+
+  .ember-application.rose-theme-light & {
+    --background-image: var(--background-image-light);
+  }
+
+  @media (prefers-color-scheme: dark) {
+    --background-image: var(--background-image-dark);
+  }
+
+  .ember-application.rose-theme-dark & {
+    --background-image: var(--background-image-dark);
+  }
+
   position: relative;
   display: inline-block;
 
@@ -59,14 +76,10 @@ $chevronWhite: "data:image/svg+xml;utf-8,<svg viewBox='0 0 24 24' fill='%23fffff
 
     &.show-caret {
       padding-right: sizing.rems(xl);
-      background-image: url($chevron);
+      background: var(--background-image);
       background-repeat: no-repeat;
       background-position: right sizing.rems(m) center;
       background-size: sizing.rems(m);
-
-      @media (prefers-color-scheme: dark) {
-        background-image: url($chevronWhite);
-      }
     }
 
     // Hide default twistie triangle
diff --git a/addons/rose/addon/styles/rose/components/dropdown/_index.scss b/addons/rose/addon/styles/rose/components/dropdown/_index.scss
index 764414ab2..ad9bba47a 100644
--- a/addons/rose/addon/styles/rose/components/dropdown/_index.scss
+++ b/addons/rose/addon/styles/rose/components/dropdown/_index.scss
@@ -2,3 +2,4 @@
 @import 'button';
 @import 'link';
 @import 'item';
+@import 'section';
diff --git a/addons/rose/addon/styles/rose/components/dropdown/_section.scss b/addons/rose/addon/styles/rose/components/dropdown/_section.scss
new file mode 100644
index 000000000..1d3e314c0
--- /dev/null
+++ b/addons/rose/addon/styles/rose/components/dropdown/_section.scss
@@ -0,0 +1,13 @@
+@use '../../variables/sizing';
+@use '../../utilities/type';
+
+.rose-dropdown-section {
+  .rose-dropdown-section-title {
+    @include type.type(s, bold);
+    padding: 0 sizing.rems(s);
+    margin: 0;
+    $line-height: 36 / 14;
+    line-height: $line-height;
+    color: var(--ui-gray)
+  }
+}
diff --git a/addons/rose/addon/styles/rose/components/header/_index.scss b/addons/rose/addon/styles/rose/components/header/_index.scss
index 8885c0207..1bc82b5e3 100644
--- a/addons/rose/addon/styles/rose/components/header/_index.scss
+++ b/addons/rose/addon/styles/rose/components/header/_index.scss
@@ -9,15 +9,29 @@
 @import 'dropdown';
 
 .rose-header {
+
+  --box-shadow-light: none;
+  --box-shadow-dark: inset 0 -#{sizing.rems(xxxxs)} 0 var(--ui-border-subtler-1);
+
+  --box-shadow: var(--box-shadow-light);
+
+  .ember-application.rose-theme-light & {
+    --box-shadow: var(--box-shadow-light);
+  }
+
+  @media (prefers-color-scheme: dark) {
+    --box-shadow: var(--box-shadow-dark);
+  }
+
+  .ember-application.rose-theme-dark & {
+    --box-shadow: var(--box-shadow-dark);
+  }
+
   display: grid;
   grid-template-areas: 'brand nav utilities';
   grid-template-columns: 0.01fr auto 1fr;
   background: var(--black);
-  box-shadow: inset 0 -#{sizing.rems(xxxxs)} 0 var(--ui-border-subtler-1);
-
-  @media (prefers-color-scheme: light) {
-    box-shadow: none;
-  }
+  box-shadow: var(--box-shadow);
 }
 
 @media (max-width: media.width(small)) {
diff --git a/addons/rose/addon/styles/rose/variables/_opacity.scss b/addons/rose/addon/styles/rose/variables/_opacity.scss
index 28b029277..618d26a34 100644
--- a/addons/rose/addon/styles/rose/variables/_opacity.scss
+++ b/addons/rose/addon/styles/rose/variables/_opacity.scss
@@ -4,7 +4,7 @@
  */
 
 // Light Mode
-:root {
+@mixin light-mode {
   --opacity-5: 0.025;
   --opacity-4: 0.05;
   --opacity-3: 0.1;
@@ -15,12 +15,26 @@
 // Dark Mode
 // Subtler opacities look better in dark mode, so these are halved compared to
 // light mode.
+@mixin dark-mode {
+  --opacity-5: 0.0125;
+  --opacity-4: 0.0125;
+  --opacity-3: 0.025;
+  --opacity-2: 0.025;
+  --opacity-1: 0.125;
+}
+
+// Light mode is the default, hence it is applied to `html` by default
+.ember-application,
+.ember-application.rose-theme-light {
+  @include light-mode;
+}
+
 @media (prefers-color-scheme: dark) {
-  :root {
-    --opacity-5: 0.0125;
-    --opacity-4: 0.0125;
-    --opacity-3: 0.025;
-    --opacity-2: 0.025;
-    --opacity-1: 0.125;
+  .ember-application {
+    @include dark-mode;
   }
 }
+
+.ember-application.rose-theme-dark {
+  @include dark-mode;
+}
diff --git a/addons/rose/addon/styles/rose/variables/color/_css.scss b/addons/rose/addon/styles/rose/variables/color/_css.scss
index 5c910e93a..3e554cc07 100644
--- a/addons/rose/addon/styles/rose/variables/color/_css.scss
+++ b/addons/rose/addon/styles/rose/variables/color/_css.scss
@@ -4,7 +4,7 @@
  */
 
 // Light Mode
-:root {
+@mixin light-mode {
   // absolutes
   --white: #{color(white)};
   --black: #{color(black)};
@@ -80,62 +80,76 @@
 }
 
 // Dark Mode
+@mixin dark-mode {
+  // poles
+  --subtle: var(--black);
+  --stark: #{color(ui-gray, 100)};
+  --stark-components: 255, 255, 255;
+
+  // theme colors
+  --info-subtler-3: #{color(blue, 800)};
+  --info-subtler-2: #{color(blue, 700)};
+  --info-subtler-1: #{color(blue, 600)};
+  --info: #{color(blue)};
+  --info-starker-1: #{color(blue, 300)};
+  --info-starker-2: #{color(blue, 200)};
+
+  --alert-subtler-2: #{color(orange, 900)};
+  --alert-subtler-1: #{color(orange, 800)};
+  --alert: #{color(orange)};
+  --alert-starker-1: #{color(orange, 200)};
+
+  --warning-subtler-2: #{color(yellow, 900)};
+  --warning-subtler-1: #{color(yellow, 800)};
+  --warning: #{color(yellow)};
+  --warning-starker-1: #{color(yellow, 200)};
+
+  --failure-subtler-2: #{color(red, 900)};
+  --failure-subtler-1: #{color(red, 800)};
+  --failure: #{color(red, 300)};
+  --failure-starker-1: #{color(red, 200)};
+
+  --success-subtler-2: #{color(green, 900)};
+  --success-subtler-1: #{color(green, 800)};
+  --success: #{color(green, 700)};
+  --success-starker-1: #{color(green, 400)};
+
+  --action-subtler-2: #{darken(color(blue, 900), 10%)};
+  --action-subtler-1h: #{darken(color(blue, 900), 5%)};
+  --action-subtler-1: #{color(blue, 800)};
+  --action: #{color(blue, 400)};
+  --action-starker-1: #{color(blue, 200)};
+
+  --ui-border-subtler-1: #{color(ui-gray, 800)};
+  --ui-border: #{color(ui-gray, 700)};
+
+  --ui-gray-subtler-6: #{color(ui-gray, 900)};
+  --ui-gray-subtler-5: #{color(ui-gray, 800)};
+  --ui-gray-subtler-4: #{color(ui-gray, 700)};
+  --ui-gray-subtler-3: #{color(ui-gray, 600)};
+  --ui-gray-subtler-2: #{color(ui-gray, 500)};
+  --ui-gray-subtler-1: #{color(ui-gray, 400)};
+  --ui-gray: #{color(ui-gray, 300)};
+  --ui-gray-starker-1: #{color(ui-gray, 200)};
+  --ui-gray-starker-2: #{color(ui-gray, 100)};
+  --ui-gray-starker-3: #{color(ui-gray, 050)};
+  --ui-gray-starker-4: #{color(ui-gray, 010)};
+
+  --ui-header-subtler: #{color(ui-cool-gray, 100)};
+}
+
+// Light mode is the default, hence it is applied to `html` by default
+.ember-application,
+.ember-application.rose-theme-light {
+  @include light-mode;
+}
+
 @media (prefers-color-scheme: dark) {
-  :root {
-    // poles
-    --subtle: var(--black);
-    --stark: #{color(ui-gray, 100)};
-    --stark-components: 255, 255, 255;
-
-    // theme colors
-    --info-subtler-3: #{color(blue, 800)};
-    --info-subtler-2: #{color(blue, 700)};
-    --info-subtler-1: #{color(blue, 600)};
-    --info: #{color(blue)};
-    --info-starker-1: #{color(blue, 300)};
-    --info-starker-2: #{color(blue, 200)};
-
-    --alert-subtler-2: #{color(orange, 900)};
-    --alert-subtler-1: #{color(orange, 800)};
-    --alert: #{color(orange)};
-    --alert-starker-1: #{color(orange, 200)};
-
-    --warning-subtler-2: #{color(yellow, 900)};
-    --warning-subtler-1: #{color(yellow, 800)};
-    --warning: #{color(yellow)};
-    --warning-starker-1: #{color(yellow, 200)};
-
-    --failure-subtler-2: #{color(red, 900)};
-    --failure-subtler-1: #{color(red, 800)};
-    --failure: #{color(red, 300)};
-    --failure-starker-1: #{color(red, 200)};
-
-    --success-subtler-2: #{color(green, 900)};
-    --success-subtler-1: #{color(green, 800)};
-    --success: #{color(green, 700)};
-    --success-starker-1: #{color(green, 400)};
-
-    --action-subtler-2: #{darken(color(blue, 900), 10%)};
-    --action-subtler-1h: #{darken(color(blue, 900), 5%)};
-    --action-subtler-1: #{color(blue, 800)};
-    --action: #{color(blue, 400)};
-    --action-starker-1: #{color(blue, 200)};
-
-    --ui-border-subtler-1: #{color(ui-gray, 800)};
-    --ui-border: #{color(ui-gray, 700)};
-
-    --ui-gray-subtler-6: #{color(ui-gray, 900)};
-    --ui-gray-subtler-5: #{color(ui-gray, 800)};
-    --ui-gray-subtler-4: #{color(ui-gray, 700)};
-    --ui-gray-subtler-3: #{color(ui-gray, 600)};
-    --ui-gray-subtler-2: #{color(ui-gray, 500)};
-    --ui-gray-subtler-1: #{color(ui-gray, 400)};
-    --ui-gray: #{color(ui-gray, 300)};
-    --ui-gray-starker-1: #{color(ui-gray, 200)};
-    --ui-gray-starker-2: #{color(ui-gray, 100)};
-    --ui-gray-starker-3: #{color(ui-gray, 050)};
-    --ui-gray-starker-4: #{color(ui-gray, 010)};
-
-    --ui-header-subtler: #{color(ui-cool-gray, 100)};
+  .ember-application {
+    @include dark-mode;
   }
 }
+
+.ember-application.rose-theme-dark {
+  @include dark-mode;
+}
diff --git a/addons/rose/app/components/rose/dropdown/section.js b/addons/rose/app/components/rose/dropdown/section.js
new file mode 100644
index 000000000..5b4572475
--- /dev/null
+++ b/addons/rose/app/components/rose/dropdown/section.js
@@ -0,0 +1 @@
+export { default } from 'rose/components/rose/dropdown/section';
\ No newline at end of file
diff --git a/addons/rose/tests/dummy/app/templates/index.hbs b/addons/rose/tests/dummy/app/templates/index.hbs
index ae646e913..75c304532 100644
--- a/addons/rose/tests/dummy/app/templates/index.hbs
+++ b/addons/rose/tests/dummy/app/templates/index.hbs
@@ -35,6 +35,11 @@
 
   <dropdown.button>Button menu item</dropdown.button>
   <dropdown.button @style="danger">Button - danger</dropdown.button>
+  <dropdown.separator />
+  
+  <dropdown.section @title="Dropdown Section Title">
+    <dropdown.link @route="index">Menu item</dropdown.link>
+  </dropdown.section>
 </Rose::Dropdown>
 
 <Rose::Dropdown @showCaret={{false}} @icon="more-horizontal" as |dropdown|>
diff --git a/addons/rose/tests/integration/components/rose/dropdown/section-test.js b/addons/rose/tests/integration/components/rose/dropdown/section-test.js
new file mode 100644
index 000000000..1719ccd6a
--- /dev/null
+++ b/addons/rose/tests/integration/components/rose/dropdown/section-test.js
@@ -0,0 +1,27 @@
+import { module, test } from 'qunit';
+import { setupRenderingTest } from 'ember-qunit';
+import { render, find } from '@ember/test-helpers';
+import { hbs } from 'ember-cli-htmlbars';
+
+module('Integration | Component | rose/dropdown/section', function(hooks) {
+  setupRenderingTest(hooks);
+
+  test('it renders', async function(assert) {
+    await render(hbs`
+      <Rose::Dropdown::Section>
+        template block text
+      </Rose::Dropdown::Section>
+    `);
+    assert.ok(find('.rose-dropdown-section'));
+    assert.equal(this.element.textContent.trim(), 'template block text');
+  });
+
+  test('it renders with optional @title', async function(assert) {
+    await render(hbs`
+      <Rose::Dropdown::Section @title="Section Title">
+        template block text
+      </Rose::Dropdown::Section>
+    `);
+    assert.equal(find('.rose-dropdown-section-title').textContent.trim(), 'Section Title');
+  });
+});
diff --git a/addons/rose/tests/integration/components/rose/form/radio/group-test.js b/addons/rose/tests/integration/components/rose/form/radio/group-test.js
index b8e6f7fc0..dfd2e4bce 100644
--- a/addons/rose/tests/integration/components/rose/form/radio/group-test.js
+++ b/addons/rose/tests/integration/components/rose/form/radio/group-test.js
@@ -52,9 +52,15 @@ module('Integration | Component | rose/form/radio/group', function (hooks) {
     assert.equal(findAll('[type="radio"]')[1].checked, false);
   });
 
-  test('it reflects active radiofield value in @selectedValue', async function (assert) {
+  test('it reflects active radiofield value in @selectedValue and triggers a @changed function', async function (assert) {
+    assert.expect(5);
+    this.changed = (value) => assert.ok(value);
     await render(hbs`
-      <Rose::Form::Radio::Group @name="bird" @selectedValue={{this.selectedValue}} as |radioGroup|>
+      <Rose::Form::Radio::Group
+        @name="bird"
+        @selectedValue={{this.selectedValue}}
+        @changed={{this.changed}}
+      as |radioGroup|>
         <radioGroup.radio
           @name="bird"
           @label="Pegion"
diff --git a/ui/core/app/routes/application.js b/ui/core/app/routes/application.js
index 804c2896e..6d4eee236 100644
--- a/ui/core/app/routes/application.js
+++ b/ui/core/app/routes/application.js
@@ -26,6 +26,11 @@ export default class ApplicationRoute extends Route.extend(
 
   // =methods
 
+  beforeModel() {
+    const theme = this.session.get('data.theme');
+    this.toggleTheme(theme);
+  }
+
   /**
    * After becoming authenticated, does nothing.  This overrides the default
    * behavior of the ApplicationRouteMixin, which is to redirect after auth.
@@ -115,4 +120,29 @@ export default class ApplicationRoute extends Route.extend(
     }
   }
 
+  /**
+   * Applies the specified color theme to the root ember element.
+   * @param {string} theme - "light", "dark", or nullish (system default)
+   */
+  @action
+  toggleTheme(theme) {
+    const rootElementSelector = getOwner(this).rootElement;
+    const rootEl = getOwner(this).lookup('service:-document')
+      .querySelector(rootElementSelector);
+    this.session.set('data.theme', theme);
+    switch (theme) {
+      case 'light':
+        rootEl.classList.add('rose-theme-light');
+        rootEl.classList.remove('rose-theme-dark');
+        break;
+      case 'dark':
+        rootEl.classList.add('rose-theme-dark');
+        rootEl.classList.remove('rose-theme-light');
+        break;
+      default:
+        rootEl.classList.remove('rose-theme-dark');
+        rootEl.classList.remove('rose-theme-light');
+    }
+  }
+
 }
diff --git a/ui/core/app/templates/application.hbs b/ui/core/app/templates/application.hbs
index 50a823972..4602a5bd3 100644
--- a/ui/core/app/templates/application.hbs
+++ b/ui/core/app/templates/application.hbs
@@ -23,11 +23,35 @@
               {{t 'actions.change-password'}}
             </dropdown.link>
             <dropdown.separator />
+
             <dropdown.button
               {{on "click" (route-action "invalidateSession")}}
             >
               {{t 'actions.deauthenticate'}}
             </dropdown.button>
+
+            <dropdown.separator />
+
+            <dropdown.section @title={{t "titles.toggle-color-theme"}}>
+              <Rose::Form as |form|>
+                <form.radioGroup
+                  @name="theme"
+                  @selectedValue={{this.session.data.theme}}
+                  @changed={{route-action "toggleTheme"}}
+                as |radioGroup|>
+                  <dropdown.item>
+                    <radioGroup.radio @label={{t "themes.system"}} />
+                  </dropdown.item>
+                  <dropdown.item>
+                    <radioGroup.radio @label={{t "themes.light"}} @value="light" />
+                  </dropdown.item>
+                  <dropdown.item>
+                    <radioGroup.radio @label={{t "themes.dark"}} @value="dark" />
+                  </dropdown.item>
+                </form.radioGroup>
+              </Rose::Form>
+            </dropdown.section>
+
           </utilities.dropdown>
         </header.utilities>
 
diff --git a/ui/core/tests/acceptance/authentication-test.js b/ui/core/tests/acceptance/authentication-test.js
index e4965ce8e..9de13e9c8 100644
--- a/ui/core/tests/acceptance/authentication-test.js
+++ b/ui/core/tests/acceptance/authentication-test.js
@@ -6,6 +6,7 @@ import {
   click,
   find,
   findAll,
+  getRootElement
   //setupOnerror,
 } from '@ember/test-helpers';
 import { setupApplicationTest } from 'ember-qunit';
@@ -315,4 +316,29 @@ module('Acceptance | authentication', function (hooks) {
       'Session is unauthenticated, after encountering 401'
     );
   });
+
+  test('color theme is applied from session data', async function (assert) {
+    assert.expect(12);
+    authenticateSession({ scope: { id: globalScope.id, type: globalScope.type } });
+    // system default
+    await visit(orgsURL);
+    assert.notOk(currentSession().get('data.theme'));
+    assert.notOk(getRootElement().classList.contains('rose-theme-light'));
+    assert.notOk(getRootElement().classList.contains('rose-theme-dark'));
+    // toggle light mode
+    await click('[name="theme"][value="light"]');
+    assert.equal(currentSession().get('data.theme'), 'light');
+    assert.ok(getRootElement().classList.contains('rose-theme-light'));
+    assert.notOk(getRootElement().classList.contains('rose-theme-dark'));
+    // toggle dark mode
+    await click('[name="theme"][value="dark"]');
+    assert.equal(currentSession().get('data.theme'), 'dark');
+    assert.notOk(getRootElement().classList.contains('rose-theme-light'));
+    assert.ok(getRootElement().classList.contains('rose-theme-dark'));
+    // toggle system default
+    await click('[name="theme"][value=""]');
+    assert.notOk(currentSession().get('data.theme'));
+    assert.notOk(getRootElement().classList.contains('rose-theme-light'));
+    assert.notOk(getRootElement().classList.contains('rose-theme-dark'));
+  });
 });
diff --git a/ui/core/translations/en-us.yaml b/ui/core/translations/en-us.yaml
index d208e7102..c1d3bd392 100644
--- a/ui/core/translations/en-us.yaml
+++ b/ui/core/translations/en-us.yaml
@@ -19,9 +19,14 @@ titles:
   actions: Actions
   documentation: Documentation
   abandon-confirm: Discard unsaved changes?
+  toggle-color-theme: Toggle Color Theme
 descriptions:
   empty-set: There are no items to display yet.  You may be able to add items or try back later.
 questions:
   delete-confirm: Are you sure you want to delete this resource?
   remove-confirm: Are you sure you want to remove this association?
   abandon-confirm: Are you sure you want to navigate away?  Your unsaved changes will be lost.
+themes:
+  system: System Default
+  light: Light
+  dark: Dark