diff --git a/frontend/src/core/components/tools/addPageNumbers/PageNumberPreview.module.css b/frontend/src/core/components/tools/addPageNumbers/PageNumberPreview.module.css
index 1657472b1..eff81e632 100644
--- a/frontend/src/core/components/tools/addPageNumbers/PageNumberPreview.module.css
+++ b/frontend/src/core/components/tools/addPageNumbers/PageNumberPreview.module.css
@@ -8,7 +8,7 @@
 }
 
 .containerWithThumbnail {
-  background-color: transparent;
+  background-color: white;
 }
 
 .containerWithoutThumbnail {
@@ -27,6 +27,7 @@
   height: 100%;
   object-fit: contain;
   filter: grayscale(10%) contrast(95%) brightness(105%);
+  opacity: 0.3;
 }
 
 /* Quick grid overlay styles - EXACT copy from stamp */
diff --git a/frontend/src/core/components/tools/addPageNumbers/PageNumberPreview.tsx b/frontend/src/core/components/tools/addPageNumbers/PageNumberPreview.tsx
index 8edb8fa2c..7bf0dab04 100644
--- a/frontend/src/core/components/tools/addPageNumbers/PageNumberPreview.tsx
+++ b/frontend/src/core/components/tools/addPageNumbers/PageNumberPreview.tsx
@@ -181,7 +181,7 @@ export default function PageNumberPreview({ parameters, onParameterChange, file,
     position: 'relative' as const,
     width: '100%',
     aspectRatio: `${(pageSize?.widthPts ?? 595.28) / (pageSize?.heightPts ?? 841.89)} / 1`,
-    backgroundColor: pageThumbnail ? 'transparent' : 'rgba(255,255,255,0.03)',
+    backgroundColor: pageThumbnail ? 'white' : 'rgba(255,255,255,0.03)',
     border: '1px solid var(--border-default, #333)',
     overflow: 'hidden' as const
   }), [pageSize, pageThumbnail]);
diff --git a/frontend/src/core/components/tools/addStamp/StampPreview.module.css b/frontend/src/core/components/tools/addStamp/StampPreview.module.css
index 779d7bf1d..7e740f6f5 100644
--- a/frontend/src/core/components/tools/addStamp/StampPreview.module.css
+++ b/frontend/src/core/components/tools/addStamp/StampPreview.module.css
@@ -8,7 +8,7 @@
 }
 
 .containerWithThumbnail {
-  background-color: transparent;
+  background-color: white;
 }
 
 .containerWithoutThumbnail {
@@ -27,6 +27,7 @@
   height: 100%;
   object-fit: contain;
   filter: grayscale(10%) contrast(95%) brightness(105%);
+  opacity: 0.3;
 }
 
 /* Stamp item styles */
diff --git a/frontend/src/core/components/tools/addStamp/StampPreviewUtils.ts b/frontend/src/core/components/tools/addStamp/StampPreviewUtils.ts
index 67124482a..768df7120 100644
--- a/frontend/src/core/components/tools/addStamp/StampPreviewUtils.ts
+++ b/frontend/src/core/components/tools/addStamp/StampPreviewUtils.ts
@@ -209,7 +209,7 @@ export function computeStampPreviewStyle(
       position: 'relative',
       width: '100%',
       aspectRatio: `${(pageSize?.widthPts ?? 595.28) / (pageSize?.heightPts ?? 841.89)} / 1`,
-      backgroundColor: hasPageThumbnail ? 'transparent' : 'rgba(255,255,255,0.03)',
+      backgroundColor: hasPageThumbnail ? 'white' : 'rgba(255,255,255,0.03)',
       border: '1px solid var(--border-default, #333)',
       overflow: 'hidden'
     },