diff --git a/app/assets/javascripts/editor/evaluation.js b/app/assets/javascripts/editor/evaluation.js
index f4c8c41a..317a3a86 100644
--- a/app/assets/javascripts/editor/evaluation.js
+++ b/app/assets/javascripts/editor/evaluation.js
@@ -221,7 +221,7 @@ CodeOceanEditorEvaluation = {
 
         if (sanitizedStdout === '' && sanitizedStderr === '') {
             if (colorize) {
-                pre.addClass('text-muted');
+                pre.addClass('text-body-secondary');
             }
             pre.text($('#output').data('message-no-output'))
         }
diff --git a/app/assets/javascripts/shell.js b/app/assets/javascripts/shell.js
index 46d3fd28..5e64c5d2 100644
--- a/app/assets/javascripts/shell.js
+++ b/app/assets/javascripts/shell.js
@@ -67,7 +67,7 @@ $(document).on('turbolinks:load', function () {
 
             if (!output.stdout && !output.stderr) {
                 const element = $('<p>');
-                element.addClass('text-muted');
+                element.addClass('text-body-secondary');
                 element.text(log.data('message-no-output'));
                 log.append(element);
             }
@@ -164,7 +164,7 @@ $(document).on('turbolinks:load', function () {
 
     const sudo = $('#sudo');
     sudo.on('change', function () {
-        sudo.parent().toggleClass('text-muted')
+        sudo.parent().toggleClass('text-body-secondary')
         command.focus();
     });
     $('#reload-files').on('click', function () {
diff --git a/app/views/execution_environments/shell.html.slim b/app/views/execution_environments/shell.html.slim
index 1f63706f..bb7416cc 100644
--- a/app/views/execution_environments/shell.html.slim
+++ b/app/views/execution_environments/shell.html.slim
@@ -3,7 +3,7 @@ h1 = @execution_environment
 #shell data-message-timeout=t('exercises.editor.timeout', permitted_execution_time: @execution_environment.permitted_execution_time) data-message-out-of-memory=t('exercises.editor.out_of_memory',  memory_limit: @execution_environment.memory_limit) data-id=@execution_environment.id
   label.form-label for='command' = t('execution_environments.shell.command')
   .input-group.mb-3
-    .input-group-text.form-switch.ps-5 class=('text-muted' unless @execution_environment.privileged_execution?)
+    .input-group-text.form-switch.ps-5 class=('text-body-secondary' unless @execution_environment.privileged_execution?)
       input#sudo.form-check-input.mt-0 type='checkbox' disabled=('disabled' if @execution_environment.privileged_execution?)  checked=('checked' if @execution_environment.privileged_execution?)
       label.ms-2 for='sudo' = 'sudo'
     input#command.form-control type='text'
@@ -22,7 +22,7 @@ h1 = @execution_environment
           span.mx-1 = t('execution_environments.shell.file_tree.empty')
           button#reload-now-link.btn.btn-link.p-0.m-0.border-0 = t('execution_environments.shell.file_tree.list_now')
       - unless @execution_environment.privileged_execution?
-        .card-footer.justify-content-center.align-items-center.d-flex.text-muted
+        .card-footer.justify-content-center.align-items-center.d-flex.text-body-secondary
           i.fa-solid.fa-info
           span.ms-2 = t('execution_environments.shell.file_tree.root_notice')
 
diff --git a/app/views/external_users/show.html.slim b/app/views/external_users/show.html.slim
index f44e9ca5..704f24f1 100644
--- a/app/views/external_users/show.html.slim
+++ b/app/views/external_users/show.html.slim
@@ -23,7 +23,7 @@ h1 = @user.displayname
             - if study_group_membership.study_group_id == current_user.current_study_group_id
               span.text-success =< t('users.show.current_study_group')
             - else
-              =< link_to(t('users.show.set_as_current_study_group'), set_as_current_study_group_path(study_group_membership.study_group), method: :post, class: 'text-muted')
+              =< link_to(t('users.show.set_as_current_study_group'), set_as_current_study_group_path(study_group_membership.study_group), method: :post, class: 'text-body-secondary')
           - elsif @user == current_user && study_group_membership.role_teacher? && study_group_membership.study_group_id == current_user.current_study_group_id
             | ,
             span.text-success =< t('users.show.current_study_group')
diff --git a/app/views/internal_users/show.html.slim b/app/views/internal_users/show.html.slim
index b260cb62..91efdf7c 100644
--- a/app/views/internal_users/show.html.slim
+++ b/app/views/internal_users/show.html.slim
@@ -23,7 +23,7 @@ h1
             - if study_group_membership.study_group_id == current_user.current_study_group_id
               span.text-success =< t('users.show.current_study_group')
             - else
-              =< link_to(t('users.show.set_as_current_study_group'), set_as_current_study_group_path(study_group_membership.study_group), method: :post, class: 'text-muted')
+              =< link_to(t('users.show.set_as_current_study_group'), set_as_current_study_group_path(study_group_membership.study_group), method: :post, class: 'text-body-secondary')
           | )
   - else
     = t('users.show.no_groups')
diff --git a/app/views/layouts/application.html.slim b/app/views/layouts/application.html.slim
index 16c0cfce..5174f9ed 100644
--- a/app/views/layouts/application.html.slim
+++ b/app/views/layouts/application.html.slim
@@ -19,7 +19,7 @@ html lang="#{I18n.locale || I18n.default_locale}" data-default-locale="#{I18n.de
     meta name='current-user' content=current_user&.to_sentry_context&.to_json
   body
     - unless @embed_options[:hide_navbar]
-      nav.navbar.navbar-dark.bg-dark.navbar-expand-md.mb-4.py-1 role='navigation'
+      nav.navbar.bg-dark.navbar-expand-md.mb-4.py-1 role='navigation' data-bs-theme="dark"
         .container
           .navbar-brand
             i.fa-solid.fa-code