diff --git a/app/javascript/portal/portalHelpers.js b/app/javascript/portal/portalHelpers.js
index 6c0a87ffc..8b36e63f9 100644
--- a/app/javascript/portal/portalHelpers.js
+++ b/app/javascript/portal/portalHelpers.js
@@ -4,7 +4,7 @@ import Vue from 'vue';
 import PublicArticleSearch from './components/PublicArticleSearch.vue';
 import TableOfContents from './components/TableOfContents.vue';
 
-export const getHeadingsfromTheArticle = () => {
+export const getHeadingsFromTheArticle = () => {
   const rows = [];
   const articleElement = document.getElementById('cw-article-content');
   articleElement.querySelectorAll('h1, h2, h3').forEach(element => {
@@ -21,6 +21,53 @@ export const getHeadingsfromTheArticle = () => {
   return rows;
 };
 
+export const generatePortalBgColor = (portalColor, theme) => {
+  const baseColor = theme === 'dark' ? 'black' : 'white';
+  return `color-mix(in srgb, ${portalColor} 20%, ${baseColor})`;
+};
+
+export const generatePortalBg = (portalColor, theme) => {
+  const bgImage = theme === 'dark' ? 'hexagon-dark.svg' : 'hexagon-light.svg';
+  return `background: url(/assets/images/hc/${bgImage}) ${generatePortalBgColor(
+    portalColor,
+    theme
+  )}`;
+};
+
+export const generateGradientToBottom = theme => {
+  return `background-image: linear-gradient(to bottom, transparent, ${
+    theme === 'dark' ? '#151718' : 'white'
+  })`;
+};
+
+export const setPortalStyles = theme => {
+  const portalColor = window.portalConfig.portalColor;
+  const portalBgDiv = document.querySelector('#portal-bg');
+  const portalBgGradientDiv = document.querySelector('#portal-bg-gradient');
+
+  if (portalBgDiv) {
+    // Set background for #portal-bg
+    portalBgDiv.setAttribute('style', generatePortalBg(portalColor, theme));
+  }
+
+  if (portalBgGradientDiv) {
+    // Set gradient background for #portal-bg-gradient
+    portalBgGradientDiv.setAttribute('style', generateGradientToBottom(theme));
+  }
+};
+
+export const setPortalClass = theme => {
+  const portalDiv = document.querySelector('#portal');
+  portalDiv.classList.remove('light', 'dark');
+  if (!portalDiv) return;
+  portalDiv.classList.add(theme);
+};
+
+export const updateThemeStyles = theme => {
+  setPortalStyles(theme);
+  setPortalClass(theme);
+};
+
 export const InitializationHelpers = {
   navigateToLocalePage: () => {
     const allLocaleSwitcher = document.querySelector('.locale-switcher');
@@ -36,7 +83,7 @@ export const InitializationHelpers = {
     return false;
   },
 
-  initalizeSearch: () => {
+  initializeSearch: () => {
     const isSearchContainerAvailable = document.querySelector('#search-wrap');
     if (isSearchContainerAvailable) {
       new Vue({
@@ -51,7 +98,7 @@ export const InitializationHelpers = {
     if (isOnArticlePage) {
       new Vue({
         components: { TableOfContents },
-        data: { rows: getHeadingsfromTheArticle() },
+        data: { rows: getHeadingsFromTheArticle() },
         template: '<table-of-contents :rows="rows" />',
       }).$mount('#cw-hc-toc');
     }
@@ -68,13 +115,30 @@ export const InitializationHelpers = {
     });
   },
 
+  initializeTheme: () => {
+    const mediaQueryList = window.matchMedia('(prefers-color-scheme: dark)');
+    const getThemePreference = () =>
+      mediaQueryList.matches ? 'dark' : 'light';
+    const themeFromServer = window.portalConfig.theme;
+    if (themeFromServer === 'system') {
+      // Handle dynamic theme changes for system theme
+      mediaQueryList.addEventListener('change', event => {
+        const newTheme = event.matches ? 'dark' : 'light';
+        updateThemeStyles(newTheme);
+      });
+      const themePreference = getThemePreference();
+      updateThemeStyles(themePreference);
+    }
+  },
+
   initialize: () => {
     if (window.portalConfig.isPlainLayoutEnabled === 'true') {
       InitializationHelpers.appendPlainParamToURLs();
     } else {
       InitializationHelpers.navigateToLocalePage();
-      InitializationHelpers.initalizeSearch();
+      InitializationHelpers.initializeSearch();
       InitializationHelpers.initializeTableOfContents();
+      // InitializationHelpers.initializeTheme();
     }
   },
 
diff --git a/app/javascript/portal/specs/portal.spec.js b/app/javascript/portal/specs/portal.spec.js
index cd4347bad..69e1e81f0 100644
--- a/app/javascript/portal/specs/portal.spec.js
+++ b/app/javascript/portal/specs/portal.spec.js
@@ -1,4 +1,12 @@
-import { InitializationHelpers } from '../portalHelpers';
+import {
+  InitializationHelpers,
+  generatePortalBgColor,
+  generatePortalBg,
+  generateGradientToBottom,
+  setPortalStyles,
+  setPortalClass,
+  updateThemeStyles,
+} from '../portalHelpers';
 
 describe('#navigateToLocalePage', () => {
   it('returns correct cookie name', () => {
@@ -21,3 +29,198 @@ describe('#navigateToLocalePage', () => {
     );
   });
 });
+
+describe('Theme Functions', () => {
+  describe('#generatePortalBgColor', () => {
+    it('returns mixed color for dark theme', () => {
+      const result = generatePortalBgColor('#FF5733', 'dark');
+      expect(result).toBe('color-mix(in srgb, #FF5733 20%, black)');
+    });
+
+    it('returns mixed color for light theme', () => {
+      const result = generatePortalBgColor('#FF5733', 'light');
+      expect(result).toBe('color-mix(in srgb, #FF5733 20%, white)');
+    });
+  });
+
+  describe('#generatePortalBg', () => {
+    it('returns background for dark theme', () => {
+      const result = generatePortalBg('#FF5733', 'dark');
+      expect(result).toBe(
+        'background: url(/assets/images/hc/hexagon-dark.svg) color-mix(in srgb, #FF5733 20%, black)'
+      );
+    });
+
+    it('returns background for light theme', () => {
+      const result = generatePortalBg('#FF5733', 'light');
+      expect(result).toBe(
+        'background: url(/assets/images/hc/hexagon-light.svg) color-mix(in srgb, #FF5733 20%, white)'
+      );
+    });
+  });
+
+  describe('#generateGradientToBottom', () => {
+    it('returns gradient for dark theme', () => {
+      const result = generateGradientToBottom('dark');
+      expect(result).toBe(
+        'background-image: linear-gradient(to bottom, transparent, #151718)'
+      );
+    });
+
+    it('returns gradient for light theme', () => {
+      const result = generateGradientToBottom('light');
+      expect(result).toBe(
+        'background-image: linear-gradient(to bottom, transparent, white)'
+      );
+    });
+  });
+
+  describe('#setPortalStyles', () => {
+    let mockPortalBgDiv;
+    let mockPortalBgGradientDiv;
+
+    beforeEach(() => {
+      // Mocking portal background div
+      mockPortalBgDiv = document.createElement('div');
+      mockPortalBgDiv.id = 'portal-bg';
+      document.body.appendChild(mockPortalBgDiv);
+
+      // Mocking portal background gradient div
+      mockPortalBgGradientDiv = document.createElement('div');
+      mockPortalBgGradientDiv.id = 'portal-bg-gradient';
+      document.body.appendChild(mockPortalBgGradientDiv);
+    });
+
+    afterEach(() => {
+      document.body.innerHTML = '';
+    });
+
+    it('sets styles for portal background based on theme', () => {
+      window.portalConfig = { portalColor: '#FF5733' };
+
+      setPortalStyles('dark');
+      const expectedPortalBgStyle =
+        'background: url(/assets/images/hc/hexagon-dark.svg) color-mix(in srgb, #FF5733 20%, black)';
+      const expectedGradientStyle =
+        'background-image: linear-gradient(to bottom, transparent, #151718)';
+
+      expect(mockPortalBgDiv.getAttribute('style')).toBe(expectedPortalBgStyle);
+      expect(mockPortalBgGradientDiv.getAttribute('style')).toBe(
+        expectedGradientStyle
+      );
+    });
+  });
+
+  describe('#setPortalClass', () => {
+    let mockPortalDiv;
+
+    beforeEach(() => {
+      // Mocking portal div
+      mockPortalDiv = document.createElement('div');
+      mockPortalDiv.id = 'portal';
+      mockPortalDiv.classList.add('light');
+      document.body.appendChild(mockPortalDiv);
+    });
+
+    afterEach(() => {
+      document.body.innerHTML = '';
+    });
+
+    it('sets portal class based on theme', () => {
+      setPortalClass('dark');
+
+      expect(mockPortalDiv.classList.contains('dark')).toBe(true);
+      expect(mockPortalDiv.classList.contains('light')).toBe(false);
+    });
+  });
+
+  describe('#updateThemeStyles', () => {
+    let mockPortalDiv;
+    let mockPortalBgDiv;
+    let mockPortalBgGradientDiv;
+
+    beforeEach(() => {
+      // Mocking portal div
+      mockPortalDiv = document.createElement('div');
+      mockPortalDiv.id = 'portal';
+      document.body.appendChild(mockPortalDiv);
+
+      // Mocking portal background div
+      mockPortalBgDiv = document.createElement('div');
+      mockPortalBgDiv.id = 'portal-bg';
+      document.body.appendChild(mockPortalBgDiv);
+
+      // Mocking portal background gradient div
+      mockPortalBgGradientDiv = document.createElement('div');
+      mockPortalBgGradientDiv.id = 'portal-bg-gradient';
+      document.body.appendChild(mockPortalBgGradientDiv);
+    });
+
+    afterEach(() => {
+      document.body.innerHTML = '';
+    });
+
+    it('updates theme styles based on theme', () => {
+      window.portalConfig = { portalColor: '#FF5733' };
+
+      updateThemeStyles('dark');
+
+      const expectedPortalBgStyle =
+        'background: url(/assets/images/hc/hexagon-dark.svg) color-mix(in srgb, #FF5733 20%, black)';
+      const expectedGradientStyle =
+        'background-image: linear-gradient(to bottom, transparent, #151718)';
+
+      expect(mockPortalDiv.classList.contains('dark')).toBe(true);
+      expect(mockPortalBgDiv.getAttribute('style')).toBe(expectedPortalBgStyle);
+      expect(mockPortalBgGradientDiv.getAttribute('style')).toBe(
+        expectedGradientStyle
+      );
+    });
+  });
+
+  describe('#initializeTheme', () => {
+    let mockPortalDiv;
+
+    beforeEach(() => {
+      mockPortalDiv = document.createElement('div');
+      mockPortalDiv.id = 'portal';
+      document.body.appendChild(mockPortalDiv);
+    });
+
+    afterEach(() => {
+      document.body.innerHTML = '';
+    });
+
+    it('updates theme based on system preferences', () => {
+      const mediaQueryList = {
+        matches: true,
+        addEventListener: jest.fn(),
+      };
+      window.matchMedia = jest.fn().mockReturnValue(mediaQueryList);
+      window.portalConfig = { theme: 'system' };
+
+      InitializationHelpers.initializeTheme();
+
+      expect(mediaQueryList.addEventListener).toBeCalledWith(
+        'change',
+        expect.any(Function)
+      );
+      expect(mockPortalDiv.classList.contains('dark')).toBe(true);
+    });
+
+    it('does not update theme if themeFromServer is not "system"', () => {
+      const mediaQueryList = {
+        matches: true,
+        addEventListener: jest.fn(),
+      };
+      window.matchMedia = jest.fn().mockReturnValue(mediaQueryList);
+      window.portalConfig = { theme: 'dark' };
+
+      InitializationHelpers.initializeTheme();
+
+      expect(mediaQueryList.addEventListener).not.toBeCalled();
+      expect(mockPortalDiv.classList.contains('dark')).toBe(false);
+      expect(mockPortalDiv.classList.contains('light')).toBe(false);
+    });
+  });
+});
diff --git a/app/views/layouts/portal.html.erb b/app/views/layouts/portal.html.erb
index d446e2e6f..2ae188fc3 100644
--- a/app/views/layouts/portal.html.erb
+++ b/app/views/layouts/portal.html.erb
@@ -48,6 +48,8 @@ By default, it renders:
   <script>
     window.portalConfig = {
       portalSlug: '<%= @portal.slug %>',
+      portalColor: '<%= @portal.color %>',
+      theme: '<%= @theme %>',
       localeCode: '<%= @locale %>',
       searchTranslations: {
         searchPlaceholder: '<%= I18n.t('public_portal.search.search_placeholder') %>',