diff --git a/src/components/dashboard/CategoryPieChart.tsx b/src/components/dashboard/CategoryPieChart.tsx
index e7cf7ee..5283c80 100644
--- a/src/components/dashboard/CategoryPieChart.tsx
+++ b/src/components/dashboard/CategoryPieChart.tsx
@@ -43,6 +43,14 @@ export default function CategoryPieChart({ data }: CategoryPieChartProps) {
             formatter={(value) =>
               new Intl.NumberFormat("en-CA", { style: "currency", currency: "CAD" }).format(Number(value))
             }
+            contentStyle={{
+              backgroundColor: "var(--card)",
+              border: "1px solid var(--border)",
+              borderRadius: "8px",
+              color: "var(--foreground)",
+            }}
+            labelStyle={{ color: "var(--foreground)" }}
+            itemStyle={{ color: "var(--foreground)" }}
           />
         </PieChart>
       </ResponsiveContainer>
diff --git a/src/components/import/DuplicateCheckPanel.tsx b/src/components/import/DuplicateCheckPanel.tsx
index c2d57b4..15942be 100644
--- a/src/components/import/DuplicateCheckPanel.tsx
+++ b/src/components/import/DuplicateCheckPanel.tsx
@@ -151,8 +151,8 @@ export default function DuplicateCheckPanel({
                         <span
                           className={`inline-block px-2 py-0.5 text-xs rounded-full ${
                             isBatch
-                              ? "bg-amber-100 text-amber-800 dark:bg-amber-900/30 dark:text-amber-300"
-                              : "bg-blue-100 text-blue-800 dark:bg-blue-900/30 dark:text-blue-300"
+                              ? "bg-[var(--accent)]/15 text-[var(--accent)]"
+                              : "bg-[var(--primary)]/15 text-[var(--primary)]"
                           }`}
                         >
                           {isBatch
diff --git a/src/components/import/ImportConfirmation.tsx b/src/components/import/ImportConfirmation.tsx
index 8e763ca..3c9aa88 100644
--- a/src/components/import/ImportConfirmation.tsx
+++ b/src/components/import/ImportConfirmation.tsx
@@ -78,7 +78,7 @@ export default function ImportConfirmation({
 
         {/* Rows to import */}
         <div className="p-4 flex items-center gap-3">
-          <CheckCircle size={18} className="text-emerald-500" />
+          <CheckCircle size={18} className="text-[var(--positive)]" />
           <div>
             <p className="text-sm font-medium">
               {t("import.confirm.rowsToImport")}
diff --git a/src/components/import/SourceCard.tsx b/src/components/import/SourceCard.tsx
index cd28b8a..cf0114f 100644
--- a/src/components/import/SourceCard.tsx
+++ b/src/components/import/SourceCard.tsx
@@ -38,7 +38,7 @@ export default function SourceCard({
           {isConfigured && (
             <CheckCircle
               size={16}
-              className="text-emerald-500"
+              className="text-[var(--positive)]"
             />
           )}
         </div>
diff --git a/src/components/layout/Sidebar.tsx b/src/components/layout/Sidebar.tsx
index 73d6d60..dc99a36 100644
--- a/src/components/layout/Sidebar.tsx
+++ b/src/components/layout/Sidebar.tsx
@@ -10,8 +10,11 @@ import {
   BarChart3,
   Settings,
   Languages,
+  Moon,
+  Sun,
 } from "lucide-react";
 import { NAV_ITEMS, APP_NAME } from "../../shared/constants";
+import { useTheme } from "../../hooks/useTheme";
 
 const iconMap: Record<string, React.ComponentType<{ size?: number }>> = {
   LayoutDashboard,
@@ -26,6 +29,7 @@ const iconMap: Record<string, React.ComponentType<{ size?: number }>> = {
 
 export default function Sidebar() {
   const { t, i18n } = useTranslation();
+  const { theme, toggleTheme } = useTheme();
 
   const toggleLanguage = () => {
     const next = i18n.language === "fr" ? "en" : "fr";
@@ -60,7 +64,14 @@ export default function Sidebar() {
         })}
       </nav>
 
-      <div className="p-3 border-t border-white/10">
+      <div className="p-3 border-t border-white/10 space-y-1">
+        <button
+          onClick={toggleTheme}
+          className="flex items-center gap-2 w-full px-3 py-2 rounded-lg text-sm hover:bg-[var(--sidebar-hover)] transition-colors"
+        >
+          {theme === "dark" ? <Sun size={18} /> : <Moon size={18} />}
+          <span>{theme === "dark" ? t("common.lightMode") : t("common.darkMode")}</span>
+        </button>
         <button
           onClick={toggleLanguage}
           className="flex items-center gap-2 w-full px-3 py-2 rounded-lg text-sm hover:bg-[var(--sidebar-hover)] transition-colors"
diff --git a/src/components/reports/CategoryBarChart.tsx b/src/components/reports/CategoryBarChart.tsx
index b97101f..00e8a85 100644
--- a/src/components/reports/CategoryBarChart.tsx
+++ b/src/components/reports/CategoryBarChart.tsx
@@ -51,7 +51,10 @@ export default function CategoryBarChart({ data }: CategoryBarChartProps) {
               backgroundColor: "var(--card)",
               border: "1px solid var(--border)",
               borderRadius: "8px",
+              color: "var(--foreground)",
             }}
+            labelStyle={{ color: "var(--foreground)" }}
+            itemStyle={{ color: "var(--foreground)" }}
           />
           <Bar dataKey="total" name={t("dashboard.expenses")} radius={[0, 4, 4, 0]}>
             {data.map((item, index) => (
diff --git a/src/components/reports/CategoryOverTimeChart.tsx b/src/components/reports/CategoryOverTimeChart.tsx
index f969a89..7793b90 100644
--- a/src/components/reports/CategoryOverTimeChart.tsx
+++ b/src/components/reports/CategoryOverTimeChart.tsx
@@ -59,7 +59,10 @@ export default function CategoryOverTimeChart({ data }: CategoryOverTimeChartPro
               backgroundColor: "var(--card)",
               border: "1px solid var(--border)",
               borderRadius: "8px",
+              color: "var(--foreground)",
             }}
+            labelStyle={{ color: "var(--foreground)" }}
+            itemStyle={{ color: "var(--foreground)" }}
           />
           <Legend />
           {data.categories.map((name) => (
diff --git a/src/components/reports/MonthlyTrendsChart.tsx b/src/components/reports/MonthlyTrendsChart.tsx
index 6921680..1b2f9ac 100644
--- a/src/components/reports/MonthlyTrendsChart.tsx
+++ b/src/components/reports/MonthlyTrendsChart.tsx
@@ -68,7 +68,10 @@ export default function MonthlyTrendsChart({ data }: MonthlyTrendsChartProps) {
               backgroundColor: "var(--card)",
               border: "1px solid var(--border)",
               borderRadius: "8px",
+              color: "var(--foreground)",
             }}
+            labelStyle={{ color: "var(--foreground)" }}
+            itemStyle={{ color: "var(--foreground)" }}
           />
           <Area
             type="monotone"
diff --git a/src/hooks/useTheme.ts b/src/hooks/useTheme.ts
new file mode 100644
index 0000000..544206c
--- /dev/null
+++ b/src/hooks/useTheme.ts
@@ -0,0 +1,42 @@
+import { useState, useEffect, useCallback } from "react";
+
+type Theme = "light" | "dark";
+
+const STORAGE_KEY = "theme";
+
+function getInitialTheme(): Theme {
+  const stored = localStorage.getItem(STORAGE_KEY);
+  if (stored === "light" || stored === "dark") return stored;
+  return window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light";
+}
+
+function applyTheme(theme: Theme) {
+  document.documentElement.classList.toggle("dark", theme === "dark");
+}
+
+export function useTheme() {
+  const [theme, setTheme] = useState<Theme>(getInitialTheme);
+
+  useEffect(() => {
+    applyTheme(theme);
+    localStorage.setItem(STORAGE_KEY, theme);
+  }, [theme]);
+
+  // Listen for OS preference changes (only when no explicit user choice)
+  useEffect(() => {
+    const mq = window.matchMedia("(prefers-color-scheme: dark)");
+    const handler = (e: MediaQueryListEvent) => {
+      if (!localStorage.getItem(STORAGE_KEY)) {
+        setTheme(e.matches ? "dark" : "light");
+      }
+    };
+    mq.addEventListener("change", handler);
+    return () => mq.removeEventListener("change", handler);
+  }, []);
+
+  const toggleTheme = useCallback(() => {
+    setTheme((prev) => (prev === "light" ? "dark" : "light"));
+  }, []);
+
+  return { theme, toggleTheme } as const;
+}
diff --git a/src/i18n/locales/en.json b/src/i18n/locales/en.json
index 776f98c..2fb07c3 100644
--- a/src/i18n/locales/en.json
+++ b/src/i18n/locales/en.json
@@ -362,6 +362,8 @@
     "noResults": "No results",
     "confirm": "Confirm",
     "language": "Language",
-    "total": "Total"
+    "total": "Total",
+    "darkMode": "Dark mode",
+    "lightMode": "Light mode"
   }
 }
diff --git a/src/i18n/locales/fr.json b/src/i18n/locales/fr.json
index 46d2156..ac3045d 100644
--- a/src/i18n/locales/fr.json
+++ b/src/i18n/locales/fr.json
@@ -362,6 +362,8 @@
     "noResults": "Aucun résultat",
     "confirm": "Confirmer",
     "language": "Langue",
-    "total": "Total"
+    "total": "Total",
+    "darkMode": "Mode sombre",
+    "lightMode": "Mode clair"
   }
 }
diff --git a/src/pages/BudgetPage.tsx b/src/pages/BudgetPage.tsx
index b6f3d69..a6e4898 100644
--- a/src/pages/BudgetPage.tsx
+++ b/src/pages/BudgetPage.tsx
@@ -39,7 +39,7 @@ export default function BudgetPage() {
       </div>
 
       {error && (
-        <div className="mb-4 p-3 rounded-lg bg-red-100 text-red-800 text-sm border border-red-200">
+        <div className="mb-4 p-3 rounded-lg bg-[var(--negative)]/10 text-[var(--negative)] text-sm border border-[var(--negative)]/20">
           {error}
         </div>
       )}
diff --git a/src/pages/ReportsPage.tsx b/src/pages/ReportsPage.tsx
index 05d0226..3383ed4 100644
--- a/src/pages/ReportsPage.tsx
+++ b/src/pages/ReportsPage.tsx
@@ -40,7 +40,7 @@ export default function ReportsPage() {
       </div>
 
       {state.error && (
-        <div className="bg-red-100 text-red-700 rounded-xl p-4 mb-6">
+        <div className="bg-[var(--negative)]/10 text-[var(--negative)] rounded-xl p-4 mb-6">
           {state.error}
         </div>
       )}
diff --git a/src/pages/SettingsPage.tsx b/src/pages/SettingsPage.tsx
index fc2c89e..6a89641 100644
--- a/src/pages/SettingsPage.tsx
+++ b/src/pages/SettingsPage.tsx
@@ -45,7 +45,7 @@ export default function SettingsPage() {
           </div>
           <div>
             <h2 className="text-lg font-semibold">{APP_NAME}</h2>
-            <p className="text-sm text-[var(--muted)]">
+            <p className="text-sm text-[var(--muted-foreground)]">
               {t("settings.version", { version })}
             </p>
           </div>
@@ -72,7 +72,7 @@ export default function SettingsPage() {
 
         {/* checking */}
         {state.status === "checking" && (
-          <div className="flex items-center gap-2 text-[var(--muted)]">
+          <div className="flex items-center gap-2 text-[var(--muted-foreground)]">
             <Loader2 size={16} className="animate-spin" />
             {t("settings.updates.checking")}
           </div>
@@ -87,7 +87,7 @@ export default function SettingsPage() {
             </div>
             <button
               onClick={checkForUpdate}
-              className="text-sm text-[var(--muted)] hover:text-[var(--foreground)] transition-colors"
+              className="text-sm text-[var(--muted-foreground)] hover:text-[var(--foreground)] transition-colors"
             >
               <RefreshCw size={14} />
             </button>
@@ -113,7 +113,7 @@ export default function SettingsPage() {
         {/* downloading */}
         {state.status === "downloading" && (
           <div className="space-y-2">
-            <div className="flex items-center gap-2 text-[var(--muted)]">
+            <div className="flex items-center gap-2 text-[var(--muted-foreground)]">
               <Loader2 size={16} className="animate-spin" />
               {t("settings.updates.downloading")}
               {progressPercent !== null && <span>{progressPercent}%</span>}
@@ -145,7 +145,7 @@ export default function SettingsPage() {
 
         {/* installing */}
         {state.status === "installing" && (
-          <div className="flex items-center gap-2 text-[var(--muted)]">
+          <div className="flex items-center gap-2 text-[var(--muted-foreground)]">
             <Loader2 size={16} className="animate-spin" />
             {t("settings.updates.installing")}
           </div>
@@ -158,7 +158,7 @@ export default function SettingsPage() {
               <AlertCircle size={16} />
               {t("settings.updates.error")}
             </div>
-            <p className="text-sm text-[var(--muted)]">{state.error}</p>
+            <p className="text-sm text-[var(--muted-foreground)]">{state.error}</p>
             <button
               onClick={checkForUpdate}
               className="flex items-center gap-2 px-4 py-2 border border-[var(--border)] rounded-lg hover:bg-[var(--border)] transition-colors"
@@ -171,7 +171,7 @@ export default function SettingsPage() {
       </div>
 
       {/* Data safety notice */}
-      <div className="flex items-start gap-2 text-sm text-[var(--muted)]">
+      <div className="flex items-start gap-2 text-sm text-[var(--muted-foreground)]">
         <ShieldCheck size={16} className="mt-0.5 shrink-0" />
         <p>{t("settings.dataSafeNotice")}</p>
       </div>
diff --git a/src/styles.css b/src/styles.css
index 52c2a45..ce28ec3 100644
--- a/src/styles.css
+++ b/src/styles.css
@@ -59,28 +59,35 @@
   --negative: #ef4444;
 }
 
-/* Dark mode */
+/* Dark mode — inspired by famille-website warm gray palette */
 .dark {
-  --background: #1a1a2e;
-  --foreground: var(--color-creme-100);
-  --card: #16213e;
-  --card-foreground: var(--color-creme-100);
+  --background: #111827;
+  --foreground: #f3f4f6;
+  --card: #1f2937;
+  --card-foreground: #f3f4f6;
   --primary: var(--color-bleu-400);
-  --primary-foreground: #1a1a2e;
+  --primary-foreground: #111827;
   --accent: var(--color-terracotta-400);
-  --accent-foreground: #1a1a2e;
-  --muted: #16213e;
+  --accent-foreground: #111827;
+  --muted: #374151;
   --muted-foreground: #9ca3af;
-  --border: #2a2a4a;
-  --sidebar-bg: #0f0f23;
-  --sidebar-fg: var(--color-creme-200);
-  --sidebar-hover: #16213e;
-  --sidebar-active: #1a2744;
+  --border: #374151;
+  --sidebar-bg: #0f172a;
+  --sidebar-fg: #f3f4f6;
+  --sidebar-hover: #1e293b;
+  --sidebar-active: #334155;
   --positive: #4ade80;
   --negative: #f87171;
 }
 
 /* Base styles */
+:root {
+  color-scheme: light;
+}
+.dark {
+  color-scheme: dark;
+}
+
 body {
   background-color: var(--background);
   color: var(--foreground);
@@ -89,6 +96,10 @@ body {
   min-height: 100vh;
 }
 
+*, *::before, *::after {
+  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
+}
+
 /* Scrollbar styling */
 ::-webkit-scrollbar {
   width: 6px;