diff --git a/se5/AmericanToBritish.Tests/PluginAppTests.cs b/se5/AmericanToBritish.Tests/PluginAppTests.cs
new file mode 100644
index 00000000..736f8689
--- /dev/null
+++ b/se5/AmericanToBritish.Tests/PluginAppTests.cs
@@ -0,0 +1,27 @@
+using Avalonia.Styling;
+using SubtitleEdit.Plugins.Shared;
+
+namespace AmericanToBritish.Tests;
+
+/// <summary>Plugin-Shared's theme variant choice, shared by every plugin built on PluginApp.</summary>
+public class PluginAppTests
+{
+    [Theory]
+    [InlineData("Nord", true, "Dark")]
+    [InlineData("System", true, "Dark")]
+    [InlineData("Dark", false, "Light")]
+    [InlineData("Light", false, "Light")]
+    public void ThemeColors_IsDark_Wins(string theme, bool isDark, string expected)
+    {
+        var request = new PluginRequest { Theme = theme, ThemeColors = new PluginThemeColors { IsDark = isDark } };
+        Assert.Equal(expected, PluginApp.ResolveThemeVariant(request).Key);
+    }
+
+    [Theory]
+    [InlineData("Dark", "Dark")]
+    [InlineData("dark", "Dark")]
+    [InlineData("Nord", "Light")]
+    [InlineData("", "Light")]
+    public void NoThemeColors_FallsBackToName(string theme, string expected) =>
+        Assert.Equal(expected, PluginApp.ResolveThemeVariant(new PluginRequest { Theme = theme }).Key);
+}
diff --git a/se5/Plugin-Shared/PluginApp.cs b/se5/Plugin-Shared/PluginApp.cs
index de28b9eb..7c699d35 100644
--- a/se5/Plugin-Shared/PluginApp.cs
+++ b/se5/Plugin-Shared/PluginApp.cs
@@ -25,7 +25,7 @@ public override void OnFrameworkInitializationCompleted()
 
         if (PendingRequest is not null)
         {
-            RequestedThemeVariant = ResolveThemeVariant(PendingRequest.Theme);
+            RequestedThemeVariant = ResolveThemeVariant(PendingRequest);
             PluginThemeStyles.Apply(PendingRequest.ThemeColors);
 
             if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
@@ -37,6 +37,16 @@ public override void OnFrameworkInitializationCompleted()
         base.OnFrameworkInitializationCompleted();
     }
 
+    /// <summary>
+    /// Dark or light controls to match Subtitle Edit. <see cref="PluginThemeColors.IsDark"/> wins:
+    /// it is true for every dark theme (Nord, Cinema, ...) and for "System" on a dark OS, which the
+    /// theme name alone does not tell. Older SE versions send no colors, so the name is the fallback.
+    /// </summary>
+    public static ThemeVariant ResolveThemeVariant(PluginRequest request) =>
+        request.ThemeColors is { } colors
+            ? colors.IsDark ? ThemeVariant.Dark : ThemeVariant.Light
+            : ResolveThemeVariant(request.Theme);
+
     /// <summary>Map the SE theme string ("Dark" / "Light" / "System" / ...) to an Avalonia <see cref="ThemeVariant"/>.</summary>
     public static ThemeVariant ResolveThemeVariant(string? seThemeName)
     {
diff --git a/se5/TypewriterEffect/App.axaml.cs b/se5/TypewriterEffect/App.axaml.cs
index a10904ab..7bc80a6b 100644
--- a/se5/TypewriterEffect/App.axaml.cs
+++ b/se5/TypewriterEffect/App.axaml.cs
@@ -21,9 +21,12 @@ public override void OnFrameworkInitializationCompleted()
 
         if (PendingRequest is not null)
         {
-            RequestedThemeVariant = string.Equals(PendingRequest.Theme, "Dark", System.StringComparison.OrdinalIgnoreCase)
-                ? ThemeVariant.Dark
-                : ThemeVariant.Light;
+            // IsDark covers every dark theme and "System" on a dark OS; older SE versions only send the name.
+            RequestedThemeVariant = PendingRequest.ThemeColors is { } colors
+                ? colors.IsDark ? ThemeVariant.Dark : ThemeVariant.Light
+                : string.Equals(PendingRequest.Theme, "Dark", System.StringComparison.OrdinalIgnoreCase)
+                    ? ThemeVariant.Dark
+                    : ThemeVariant.Light;
 
             PluginThemeStyles.Apply(PendingRequest.ThemeColors);