diff --git a/config/dot/hypr/looks.lua b/config/dot/hypr/looks.lua
index b8b5646..e668e26 100644
--- a/config/dot/hypr/looks.lua
+++ b/config/dot/hypr/looks.lua
@@ -29,7 +29,11 @@ hl.config({
             active_border   = { colors = { "rgba(82aaffee)", "rgba(b172b0ee)" }, angle = 115 },
             -- Unfocused windows get no colour at all. The gradient only means
             -- something if exactly one window on screen is wearing it.
-            inactive_border = "rgba(3b426199)",
+            -- Follows the colour scheme: a dark neutral is invisible against a
+            -- light desktop. services/ColorScheme.qml applies changes live;
+            -- this is the value a fresh session starts from.
+            inactive_border = prefs.get("colorScheme", "dark") == "light"
+                and "rgba(a8aecb99)" or "rgba(3b426199)",
         },
 
         resize_on_border = true,
diff --git a/config/dot/quickshell/config/PreferenceSchema.qml b/config/dot/quickshell/config/PreferenceSchema.qml
index 95eaba7..c5d89ed 100644
--- a/config/dot/quickshell/config/PreferenceSchema.qml
+++ b/config/dot/quickshell/config/PreferenceSchema.qml
@@ -386,6 +386,26 @@ Singleton {
             detail: "A time earlier than the start simply means the next morning"
         },
 
+        // ── Colour scheme ───────────────────────────────────────────────────
+        // Light is Tokyo Night Day, the official light variant, rather than a
+        // palette invented to merely not be dark. Both share the same hues at
+        // different lightness, which is what keeps the Prism identity intact
+        // across the switch.
+        //
+        // services/ColorScheme.qml pushes the choice to GTK and to the
+        // compositor's border colours, because an application toolbar or a
+        // window border still wearing the other scheme is more jarring than
+        // either scheme on its own.
+        {
+            key: "colorScheme", type: "enum", def: "dark", group: "appearance",
+            label: "Appearance",
+            detail: "Light and dark share one identity, not two themes",
+            options: [
+                { value: "dark", label: "Dark" },
+                { value: "light", label: "Light" }
+            ]
+        },
+
         // ── Typography ──────────────────────────────────────────────────────
         // The single largest thing in this desktop that used to be changeable
         // only by editing Theme.qml.
diff --git a/config/dot/quickshell/config/Theme.qml b/config/dot/quickshell/config/Theme.qml
index 7538fdf..a490e56 100644
--- a/config/dot/quickshell/config/Theme.qml
+++ b/config/dot/quickshell/config/Theme.qml
@@ -18,36 +18,47 @@ import QtQuick
 Singleton {
     id: root
 
+    // ── Colour scheme ───────────────────────────────────────────────────────
+    // Tokyo Night ships an official light variant (Day), so light mode is that
+    // rather than a palette invented to merely not be dark. The two share the
+    // same hues at different lightness, which is what lets the Prism identity
+    // survive the switch: blue still leads into orchid, it is simply a darker
+    // blue on a lighter ground.
+    //
+    // Every token below is a binding on this, so flipping it repaints the whole
+    // shell without anything needing to know it happened.
+    readonly property bool dark: DesktopPreferences.get("colorScheme") !== "light"
+
     // ── Palette ─────────────────────────────────────────────────────────────
     // Canonical Tokyo Night Moon. `accent` matches the GNOME accent exactly.
-    readonly property color bg: "#222436"
-    readonly property color bgDark: "#1e2030"
-    readonly property color bgHighlight: "#2f334d"
-    readonly property color bgPanel: "#2e2f3d" // dock glass surface
-    readonly property color bgPopover: "#21212f" // Openbar submenu background
+    readonly property color bg: root.dark ? "#222436" : "#e1e2e7"
+    readonly property color bgDark: root.dark ? "#1e2030" : "#d3d5de"
+    readonly property color bgHighlight: root.dark ? "#2f334d" : "#c4c8da"
+    readonly property color bgPanel: root.dark ? "#2e2f3d" : "#d9dae3" // dock glass surface
+    readonly property color bgPopover: root.dark ? "#21212f" : "#eaeaee" // Openbar submenu background
 
-    readonly property color fg: "#c8d3f5"
-    readonly property color fgDim: "#828bb8"
-    readonly property color fgMuted: "#636da6"
-    readonly property color gutter: "#3b4261"
+    readonly property color fg: root.dark ? "#c8d3f5" : "#3760bf"
+    readonly property color fgDim: root.dark ? "#828bb8" : "#6172b0"
+    readonly property color fgMuted: root.dark ? "#636da6" : "#848cb5"
+    readonly property color gutter: root.dark ? "#3b4261" : "#a8aecb"
 
     // The pair. `accent` is the primary and carries every state meaning
     // (focused, active, on). `accentSecondary` is the orchid from the tmux
     // theme — it never appears alone, only as the far end of a gradient. That
     // restraint is the whole point: the two colours meeting is the signature,
     // so the pink stops being special the moment it's used as a flat fill.
-    readonly property color accent: "#82aaff" // blue
-    readonly property color accentSecondary: "#b172b0" // orchid, from tmux
-    readonly property color accentAlt: "#65bcff" // blue1, a lighter blue
-    readonly property color cyan: "#86e1fc"
-    readonly property color teal: "#4fd6be"
-    readonly property color green: "#c3e88d"
-    readonly property color yellow: "#ffc777"
-    readonly property color orange: "#ff966c"
-    readonly property color red: "#ff757f"
-    readonly property color redDeep: "#c53b53"
-    readonly property color magenta: "#c099ff"
-    readonly property color pink: "#fca7ea"
+    readonly property color accent: root.dark ? "#82aaff" : "#2e7de9" // blue
+    readonly property color accentSecondary: root.dark ? "#b172b0" : "#9854f1" // orchid, from tmux
+    readonly property color accentAlt: root.dark ? "#65bcff" : "#007197" // blue1, a lighter blue
+    readonly property color cyan: root.dark ? "#86e1fc" : "#007197"
+    readonly property color teal: root.dark ? "#4fd6be" : "#118c74"
+    readonly property color green: root.dark ? "#c3e88d" : "#587539"
+    readonly property color yellow: root.dark ? "#ffc777" : "#8c6c3e"
+    readonly property color orange: root.dark ? "#ff966c" : "#b15c00"
+    readonly property color red: root.dark ? "#ff757f" : "#f52a65"
+    readonly property color redDeep: root.dark ? "#c53b53" : "#c64343"
+    readonly property color magenta: root.dark ? "#c099ff" : "#9854f1"
+    readonly property color pink: root.dark ? "#fca7ea" : "#d20065"
 
     // Semantic aliases — prefer these in widgets so intent survives a repaint.
     readonly property color ok: green
@@ -59,11 +70,14 @@ Singleton {
     // The dock sits on compositor blur, so its fill is deliberately very
     // translucent. Popovers are near-opaque because they carry text that must
     // stay legible. The bar itself has no surface or alpha token.
-    readonly property real dockAlpha: 0.34
-    readonly property real popoverAlpha: 0.92
-    readonly property real overlayAlpha: 0.55
-    readonly property real hoverAlpha: 0.14
-    readonly property real activeAlpha: 0.24
+    // Light surfaces need more opacity for the same sense of a solid panel: the
+    // same 0.34 that reads as glass over a dark desktop reads as haze over a
+    // light one, and text on it stops being legible.
+    readonly property real dockAlpha: root.dark ? 0.34 : 0.62
+    readonly property real popoverAlpha: root.dark ? 0.92 : 0.97
+    readonly property real overlayAlpha: root.dark ? 0.55 : 0.40
+    readonly property real hoverAlpha: root.dark ? 0.14 : 0.10
+    readonly property real activeAlpha: root.dark ? 0.24 : 0.18
 
     // ── Geometry ────────────────────────────────────────────────────────────
     readonly property int barHeight: 36
diff --git a/config/dot/quickshell/modules/settings/AppearancePage.qml b/config/dot/quickshell/modules/settings/AppearancePage.qml
index 2e1e456..879caef 100644
--- a/config/dot/quickshell/modules/settings/AppearancePage.qml
+++ b/config/dot/quickshell/modules/settings/AppearancePage.qml
@@ -73,6 +73,15 @@ SettingsPage {
         }
     }
 
+    SettingsCard {
+        title: "Colour scheme"
+        subtitle: ColorScheme.lastError !== ""
+            ? ColorScheme.lastError
+            : "Light is Tokyo Night Day, the official light variant — the same hues at a different lightness, so the blue-into-orchid signature survives the switch. Applications and window borders follow."
+
+        ChoiceRow { setting: "colorScheme"; divider: false }
+    }
+
     SettingsCard {
         title: "Typography"
         subtitle: Fonts.lastError !== ""
diff --git a/config/dot/quickshell/modules/settings/DesktopPreview.qml b/config/dot/quickshell/modules/settings/DesktopPreview.qml
index 0f7a30c..67acc0a 100644
--- a/config/dot/quickshell/modules/settings/DesktopPreview.qml
+++ b/config/dot/quickshell/modules/settings/DesktopPreview.qml
@@ -50,10 +50,13 @@ Rectangle {
 
     // Stands in for the wallpaper. Static: an animated gradient here would
     // repaint forever behind a settings page.
+    // Follows the colour scheme. A preview that stays dark while the shell
+    // around it is light does not read as "your desktop" -- it reads as a
+    // screenshot of someone else's.
     gradient: Gradient {
         orientation: Gradient.Vertical
-        GradientStop { position: 0.0; color: "#2b3050" }
-        GradientStop { position: 1.0; color: "#241f33" }
+        GradientStop { position: 0.0; color: Theme.dark ? "#2b3050" : "#b9c0dd" }
+        GradientStop { position: 1.0; color: Theme.dark ? "#241f33" : "#cbbcd4" }
     }
 
     // The bar, so the preview reads as this desktop and not a generic one.
@@ -203,7 +206,7 @@ Rectangle {
             shadowEnabled: true
             shadowColor: win.focused && root.glowOn
                 ? Theme.alpha(Theme.accent, 0.5)
-                : Theme.alpha("#15161e", 0.85)
+                : Theme.alpha(Theme.dark ? "#15161e" : "#6172b0", Theme.dark ? 0.85 : 0.45)
             shadowBlur: win.focused && root.glowOn
                 ? Math.min(1.0, root.px(root.glowRange) / 12)
                 : Math.min(1.0, root.px(root.shadowRange) / 24)
diff --git a/config/dot/quickshell/services/ColorScheme.qml b/config/dot/quickshell/services/ColorScheme.qml
new file mode 100644
index 0000000..4353142
--- /dev/null
+++ b/config/dot/quickshell/services/ColorScheme.qml
@@ -0,0 +1,97 @@
+pragma Singleton
+
+// Keeps everything that draws a window agreeing about light or dark.
+//
+// The shell repaints itself from Theme.qml the moment the preference changes,
+// because every token there is a binding. Two other things draw on this desktop
+// and do not read Panama's store:
+//
+//   GTK applications          read gsettings colour-scheme and gtk-theme
+//   the compositor            draws window borders and shadows
+//
+// A toolbar or a window border still wearing the other scheme is more jarring
+// than either scheme on its own, which is why this exists rather than the
+// setting simply being a Theme property.
+
+import Quickshell
+import Quickshell.Io
+import QtQuick
+import qs.config
+
+Singleton {
+    id: root
+
+    readonly property bool dark: DesktopPreferences.get("colorScheme") !== "light"
+    property string lastError: ""
+
+    // Applied one command at a time: Process runs a single command, and several
+    // of these are separate programs.
+    property var pending: []
+
+    Process {
+        id: runner
+        onExited: (exitCode, exitStatus) => {
+            if (exitCode !== 0)
+                root.lastError = "The colour scheme could not be applied everywhere.";
+            root.drain();
+        }
+    }
+
+    function drain(): void {
+        if (runner.running || root.pending.length === 0)
+            return;
+        const next = root.pending[0];
+        root.pending = root.pending.slice(1);
+        runner.exec(next);
+    }
+
+    function enqueue(commands: var): void {
+        root.pending = root.pending.concat(commands);
+        root.drain();
+    }
+
+    // Pushed once at startup as well as on change: gsettings and the compositor
+    // do not read Panama's store, so a scheme chosen in a previous session is
+    // only in effect for the shell until this runs.
+    Component.onCompleted: settle.restart()
+
+    Timer {
+        id: settle
+        interval: 1200
+        onTriggered: root.apply()
+    }
+
+    Connections {
+        target: DesktopPreferences
+        function onRevisionChanged(): void { coalesce.restart(); }
+    }
+
+    Timer {
+        id: coalesce
+        interval: 250
+        onTriggered: root.apply()
+    }
+
+    function apply(): void {
+        root.lastError = "";
+
+        const scheme = root.dark ? "prefer-dark" : "prefer-light";
+        // Adwaita's light and dark are the same theme; only the preference and
+        // the -dark suffix differ, so applications that honour either agree.
+        const gtkTheme = root.dark ? "Adwaita-dark" : "Adwaita";
+
+        const commands = [
+            ["gsettings", "set", "org.gnome.desktop.interface", "color-scheme", scheme],
+            ["gsettings", "set", "org.gnome.desktop.interface", "gtk-theme", gtkTheme]
+        ];
+
+        // Unfocused window borders. The focused border is the prism gradient and
+        // is already scheme-independent; the inactive one is a flat neutral that
+        // would be invisible against the opposite background.
+        const inactive = root.dark ? "rgba(3b426199)" : "rgba(a8aecb99)";
+        commands.push(["hyprctl", "eval",
+            `hl.config({ general = { col = { inactive_border = "${inactive}" } } })`]);
+
+        root.enqueue(commands);
+    }
+}