diff --git a/static/whiteboard.css b/static/whiteboard.css
index 20830c3..1b8a572 100644
--- a/static/whiteboard.css
+++ b/static/whiteboard.css
@@ -1,5 +1,17 @@
 /* 记事本页专属样式：全屏 textarea、悬浮工具栏、移动端适配。 */
-:root { --bar-h: 52px; }
+/* 强制浅色：本页常被 iframe 嵌入浅色站点，覆盖 common.css 的
+   color-scheme: light dark 与 prefers-color-scheme: dark，避免深色背景。 */
+:root {
+  --bar-h: 52px;
+  color-scheme: light;
+  --bg: #f6f7f9;
+  --surface: #ffffff;
+  --surface-2: rgba(0, 0, 0, 0.02);
+  --border: #e0e3e7;
+  --text: #1a1a1a;
+  --text-dim: #6b7280;
+  --shadow: 0 1px 3px rgba(0, 0, 0, 0.04), 0 1px 2px rgba(0, 0, 0, 0.06);
+}
 body { overflow: hidden; background: var(--bg); }
 .wb-app { display: flex; flex-direction: column; height: 100vh; height: 100dvh; }
 .wb-bar {
diff --git a/static/whiteboard.html b/static/whiteboard.html
index dfb95c0..7c0ca95 100644
--- a/static/whiteboard.html
+++ b/static/whiteboard.html
@@ -4,6 +4,9 @@
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
 <meta name="theme-color" content="#1565c0">
+<!-- 强制浅色：该页面会被 iframe 嵌入到浅色主题站点（mainPage），
+     禁用 common.css 的 prefers-color-scheme: dark，保持背景与嵌入站一致 -->
+<meta name="color-scheme" content="light">
 <title>记事本 - zikai</title>
 <link rel="stylesheet" href="/static/common.css">
 <link rel="stylesheet" href="/static/whiteboard.css">