diff --git a/frontend/src/api/mock/dataset.ts b/frontend/src/api/mock/dataset.ts
index 43d52cd..c6725ae 100644
--- a/frontend/src/api/mock/dataset.ts
+++ b/frontend/src/api/mock/dataset.ts
@@ -210,6 +210,7 @@ export function buildMockState(): MockState {
     if (slotIndex % 7 === 0) target = Math.max(1, shift.min_staff - 1);
     else if (slotIndex % 5 === 0) target = shift.min_staff;
     else if (slotIndex % 3 === 0) target = Math.max(shift.min_staff, shift.ideal_staff - 1);
+    else if (slotIndex % 8 === 0) target = shift.ideal_staff + 2; // sureffectif
 
     const duration = hoursBetween(shift.starts_at, shift.ends_at);
     const dateStr = shift.starts_at.slice(0, 10);
diff --git a/frontend/src/i18n/locales/fr.json b/frontend/src/i18n/locales/fr.json
index eb82266..f8cf445 100644
--- a/frontend/src/i18n/locales/fr.json
+++ b/frontend/src/i18n/locales/fr.json
@@ -85,6 +85,7 @@
   "grille.legend.critical": "SOUS-EFFECTIF CRITIQUE",
   "grille.legend.incomplete": "INCOMPLET",
   "grille.legend.complete": "COMPLET",
+  "grille.legend.overstaffed": "SUREFFECTIF",
   "grille.positionsCount": "{count} POSTES",
   "grille.assignedRequired": "AFFECTÉS / IDÉAL",
   "grille.footnote": "Chaque cellule est un créneau. Nombre = bénévoles affectés, / = effectif idéal. Cliquer ouvre le panneau d'affectation à droite.",
diff --git a/frontend/src/pages/GrillePage.tsx b/frontend/src/pages/GrillePage.tsx
index 1d5ba8d..4b4f8bb 100644
--- a/frontend/src/pages/GrillePage.tsx
+++ b/frontend/src/pages/GrillePage.tsx
@@ -83,6 +83,9 @@ export function GrillePage() {
           <LegendItem swatch="bg-paper" glyph="✓">
             {t('grille.legend.complete')}
           </LegendItem>
+          <LegendItem swatch="bg-mauve" glyph="▼">
+            {t('grille.legend.overstaffed')}
+          </LegendItem>
         </div>
       </div>
 
@@ -212,8 +215,10 @@ function PositionRow({
         }
         const assigned = shift.assigned;
         const isCrit = assigned < shift.min_staff;
-        const isInc = !isCrit && assigned < shift.ideal_staff;
-        const glyph = isCrit ? '▲' : isInc ? '◧' : '✓';
+        const isOver = assigned > shift.ideal_staff;
+        const isInc = !isCrit && !isOver && assigned < shift.ideal_staff;
+        const isOk = !isCrit && !isOver && !isInc;
+        const glyph = isCrit ? '▲' : isOver ? '▼' : isInc ? '◧' : '✓';
         const selected = selectedShiftId === shift.shift_id;
         return (
           <div
@@ -222,14 +227,15 @@ function PositionRow({
             className={cx(
               'relative flex h-9 cursor-pointer items-center justify-center gap-[3px] border-b border-r border-ink',
               isCrit && 'bg-hatch-orange',
+              isOver && 'bg-mauve hover:bg-mauve-hover',
               isInc && 'bg-yellow-soft hover:bg-yellow',
-              !isCrit && !isInc && 'bg-paper hover:bg-green/10',
+              isOk && 'bg-paper hover:bg-green/10',
             )}
             title={`${assigned} affecté(s) · min ${shift.min_staff} · idéal ${shift.ideal_staff}`}
           >
             <span className="font-mono text-[13px] font-bold">{assigned}</span>
             <span className="font-mono text-[9px] opacity-50">/{shift.ideal_staff}</span>
-            <span className={cx('font-mono text-[10px] font-bold', !isCrit && !isInc && 'text-green')}>
+            <span className={cx('font-mono text-[10px] font-bold', isOk && 'text-green')}>
               {glyph}
             </span>
             {selected ? (
diff --git a/frontend/tailwind.config.js b/frontend/tailwind.config.js
index f3a0aff..ce6863a 100644
--- a/frontend/tailwind.config.js
+++ b/frontend/tailwind.config.js
@@ -20,6 +20,8 @@ export default {
         green: '#0E9F6E',
         blue: '#A8C4FF',
         'blue-strong': '#2A6BFF', // « non publié »
+        mauve: '#CBA6E3', // état « sureffectif »
+        'mauve-hover': '#BE93D9',
       },
       fontFamily: {
         display: ['Archivo', 'Helvetica', 'Arial', 'sans-serif'],