diff --git a/crates/mdbook-html/front-end/css/variables.css b/crates/mdbook-html/front-end/css/variables.css
index af5023bc3e..861a45adf7 100644
--- a/crates/mdbook-html/front-end/css/variables.css
+++ b/crates/mdbook-html/front-end/css/variables.css
@@ -301,6 +301,8 @@
     --searchresults-li-bg: #dec2a2;
     --search-mark-bg: #e69f67;
 
+    --color-scheme: light;
+
     /* Same as `--icons` */
     --copy-button-filter: invert(51%) sepia(10%) saturate(393%) hue-rotate(198deg) brightness(86%) contrast(87%);
     /* Same as `--sidebar-active` */
diff --git a/tests/gui/books/basic/src/SUMMARY.md b/tests/gui/books/basic/src/SUMMARY.md
index 7390c82896..fa67cf3e84 100644
--- a/tests/gui/books/basic/src/SUMMARY.md
+++ b/tests/gui/books/basic/src/SUMMARY.md
@@ -1,3 +1,4 @@
 # Summary
 
 - [Chapter 1](./chapter_1.md)
+- [Chapter 2](./chapter_2.md)
diff --git a/tests/gui/books/basic/src/chapter_2.md b/tests/gui/books/basic/src/chapter_2.md
new file mode 100644
index 0000000000..785a9e090a
--- /dev/null
+++ b/tests/gui/books/basic/src/chapter_2.md
@@ -0,0 +1,10 @@
+<style>
+main {
+    background-color: light-dark(white, black);
+    color: light-dark(black, white);
+}
+</style>
+
+# title
+
+Some content
diff --git a/tests/gui/color-scheme.goml b/tests/gui/color-scheme.goml
new file mode 100644
index 0000000000..dc7c8c7a8d
--- /dev/null
+++ b/tests/gui/color-scheme.goml
@@ -0,0 +1,39 @@
+// This GUI test checks help popup.
+
+go-to: |DOC_PATH| + "basic/chapter_2.html"
+
+define-function: (
+    "change-theme",
+    [theme],
+    block {
+        store-css: ("#mdbook-theme-list", {"display": theme_list_display})
+        if: (|theme_list_display| != "block", block {
+            click: "#mdbook-theme-toggle"
+            wait-for-css: ("#mdbook-theme-list", {"display": "block"})
+        })
+        click: "#mdbook-theme-list #mdbook-theme-" + |theme|
+        wait-for: "#mdbook-theme-list #mdbook-theme-" + |theme| + ".theme-selected"
+    },
+)
+
+define-function: (
+    "check-scheme-applied",
+    [theme, background_color],
+    block {
+        call-function: ("change-theme", {"theme": |theme|})
+        assert-css: ("#mdbook-content main", {"background-color": |background_color|})
+        store-value: (themes_checked, |themes_checked| + 1)
+    }
+)
+
+store-value: (themes_checked, 1) // It's one to take into account the "auto" theme.
+
+call-function: ("check-scheme-applied", {"theme": "light", "background_color": "white"})
+call-function: ("check-scheme-applied", {"theme": "rust", "background_color": "white"})
+call-function: ("check-scheme-applied", {"theme": "coal", "background_color": "black"})
+call-function: ("check-scheme-applied", {"theme": "navy", "background_color": "black"})
+call-function: ("check-scheme-applied", {"theme": "ayu", "background_color": "black"})
+
+// We confirm that the we checked all themes. If other themes are added later on, this test will
+// fail.
+assert-count: ("#mdbook-theme-list .theme", |themes_checked|)
diff --git a/tests/gui/help.goml b/tests/gui/help.goml
index d304e773cc..fbd28c92b0 100644
--- a/tests/gui/help.goml
+++ b/tests/gui/help.goml
@@ -12,5 +12,5 @@ wait-for-css: ("#mdbook-help-container", {"display": "flex"})
 click: "#mdbook-help-popup"
 wait-for-css: ("#mdbook-help-container", {"display": "flex"})
 // Click outside dismisses.
-click: "*"
+click: (0, 0)
 wait-for-css: ("#mdbook-help-container", {"display": "none"})