diff --git a/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/color-scheme-iframe-background-mismatch-alpha.html b/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/color-scheme-iframe-background-mismatch-alpha.html
new file mode 100644
index 0000000000000..26c58198c46b0
--- /dev/null
+++ b/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/color-scheme-iframe-background-mismatch-alpha.html
@@ -0,0 +1,20 @@
+
+CSS Color Adjustment Test: iframe element with light color-scheme, frame document with dark color-scheme, :root background with alpha
+
+
+
+
+
diff --git a/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/color-scheme-iframe-background-mismatch-opaque.html b/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/color-scheme-iframe-background-mismatch-opaque.html
new file mode 100644
index 0000000000000..9e39c0b827699
--- /dev/null
+++ b/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/color-scheme-iframe-background-mismatch-opaque.html
@@ -0,0 +1,20 @@
+
+CSS Color Adjustment Test: Frames with a dark color-scheme should get an opaque background when embedding element and embedded root color-schemes do not match
+
+
+
+
+
diff --git a/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/color-scheme-iframe-background.html b/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/color-scheme-iframe-background.html
index ee0f006b5b257..591044f61803b 100644
--- a/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/color-scheme-iframe-background.html
+++ b/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/color-scheme-iframe-background.html
@@ -1,6 +1,6 @@
-CSS Color Adjustment Test: Frames with a dark color-scheme should still be transparent
-
+CSS Color Adjustment Test: Frames with a dark color-scheme should still be transparent when embedding element and embedded root color-schemes match
+
-
+
diff --git a/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/support/dark-frame-alpha.html b/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/support/dark-frame-alpha.html
new file mode 100644
index 0000000000000..cb5e6d66917e4
--- /dev/null
+++ b/testing/web-platform/tests/css/css-color-adjust/rendering/dark-color-scheme/support/dark-frame-alpha.html
@@ -0,0 +1,9 @@
+
+
+
This text should be lime and the background should be green blended with a dark canvas.