diff --git a/web/app/globals.css b/web/app/globals.css
index 452d3ad..24539f0 100644
--- a/web/app/globals.css
+++ b/web/app/globals.css
@@ -49,6 +49,40 @@
 
 :root {
   --radius: 0.65rem;
+  --background: oklch(0.985 0 0);
+  --foreground: oklch(0.205 0 0);
+  --card: oklch(1 0 0);
+  --card-foreground: oklch(0.205 0 0);
+  --popover: oklch(1 0 0);
+  --popover-foreground: oklch(0.205 0 0);
+  --primary: oklch(0.32 0 0);
+  --primary-foreground: oklch(0.985 0 0);
+  --secondary: oklch(0.96 0 0);
+  --secondary-foreground: oklch(0.24 0 0);
+  --muted: oklch(0.96 0 0);
+  --muted-foreground: oklch(0.48 0 0);
+  --accent: oklch(0.94 0 0);
+  --accent-foreground: oklch(0.24 0 0);
+  --destructive: oklch(0.59 0.225 25);
+  --border: oklch(0.89 0 0);
+  --input: oklch(0.89 0 0);
+  --ring: oklch(0.56 0 0);
+  --chart-1: oklch(0.44 0 0);
+  --chart-2: oklch(0.56 0 0);
+  --chart-3: oklch(0.68 0 0);
+  --chart-4: oklch(0.76 0 0);
+  --chart-5: oklch(0.84 0 0);
+  --sidebar: oklch(0.96 0 0);
+  --sidebar-foreground: oklch(0.24 0 0);
+  --sidebar-primary: oklch(0.32 0 0);
+  --sidebar-primary-foreground: oklch(0.985 0 0);
+  --sidebar-accent: oklch(0.92 0 0);
+  --sidebar-accent-foreground: oklch(0.24 0 0);
+  --sidebar-border: oklch(0.87 0 0);
+  --sidebar-ring: oklch(0.56 0 0);
+}
+
+:root[data-palette="green"] {
   --background: oklch(0.973 0.011 112);
   --foreground: oklch(0.22 0.021 210);
   --card: oklch(0.996 0.004 105);
@@ -151,6 +185,40 @@
 }
 
 .dark {
+  --background: oklch(0.18 0 0);
+  --foreground: oklch(0.94 0 0);
+  --card: oklch(0.225 0 0);
+  --card-foreground: oklch(0.94 0 0);
+  --popover: oklch(0.225 0 0);
+  --popover-foreground: oklch(0.94 0 0);
+  --primary: oklch(0.82 0 0);
+  --primary-foreground: oklch(0.18 0 0);
+  --secondary: oklch(0.285 0 0);
+  --secondary-foreground: oklch(0.94 0 0);
+  --muted: oklch(0.285 0 0);
+  --muted-foreground: oklch(0.7 0 0);
+  --accent: oklch(0.32 0 0);
+  --accent-foreground: oklch(0.94 0 0);
+  --destructive: oklch(0.68 0.19 25);
+  --border: oklch(1 0 0 / 10%);
+  --input: oklch(1 0 0 / 14%);
+  --ring: oklch(0.62 0 0);
+  --chart-1: oklch(0.82 0 0);
+  --chart-2: oklch(0.72 0 0);
+  --chart-3: oklch(0.62 0 0);
+  --chart-4: oklch(0.52 0 0);
+  --chart-5: oklch(0.42 0 0);
+  --sidebar: oklch(0.16 0 0);
+  --sidebar-foreground: oklch(0.93 0 0);
+  --sidebar-primary: oklch(0.82 0 0);
+  --sidebar-primary-foreground: oklch(0.18 0 0);
+  --sidebar-accent: oklch(0.27 0 0);
+  --sidebar-accent-foreground: oklch(0.94 0 0);
+  --sidebar-border: oklch(1 0 0 / 9%);
+  --sidebar-ring: oklch(0.62 0 0);
+}
+
+.dark[data-palette="green"] {
   --background: oklch(0.18 0.016 190);
   --foreground: oklch(0.94 0.009 155);
   --card: oklch(0.225 0.018 190);
diff --git a/web/app/layout.tsx b/web/app/layout.tsx
index 7dbf7fd..130fa8b 100644
--- a/web/app/layout.tsx
+++ b/web/app/layout.tsx
@@ -26,9 +26,9 @@ const geistMono = Geist_Mono({
 const paletteScript = `
 try {
   var palette = window.localStorage.getItem("dashboard_palette");
-  document.documentElement.dataset.palette = palette === "blue" || palette === "gray" ? palette : "green";
+  document.documentElement.dataset.palette = palette === "plain" || palette === "blue" || palette === "green" || palette === "gray" ? palette : "plain";
 } catch (_) {
-  document.documentElement.dataset.palette = "green";
+  document.documentElement.dataset.palette = "plain";
 }
 `
 
diff --git a/web/components/palette-toggle.test.mjs b/web/components/palette-toggle.test.mjs
new file mode 100644
index 0000000..b54e637
--- /dev/null
+++ b/web/components/palette-toggle.test.mjs
@@ -0,0 +1,28 @@
+import assert from "node:assert/strict"
+import { readFile } from "node:fs/promises"
+import test from "node:test"
+
+const paletteSource = await readFile(
+  new URL("./palette-toggle.tsx", import.meta.url),
+  "utf8",
+)
+const layoutSource = await readFile(new URL("../app/layout.tsx", import.meta.url), "utf8")
+const zhMessages = JSON.parse(
+  await readFile(new URL("../messages/zh-CN.json", import.meta.url), "utf8"),
+)
+const enMessages = JSON.parse(
+  await readFile(new URL("../messages/en-US.json", import.meta.url), "utf8"),
+)
+
+test("plain palette is the default dashboard palette", () => {
+  assert.match(paletteSource, /type PaletteMode = "plain" \| "blue" \| "green" \| "gray"/)
+  assert.match(paletteSource, /const DEFAULT_PALETTE: PaletteMode = "plain"/)
+  assert.match(layoutSource, /palette === "plain"/)
+  assert.match(layoutSource, /: "plain"/)
+})
+
+test("plain palette is available in the palette menu and messages", () => {
+  assert.match(paletteSource, /value: "plain"[\s\S]*labelKey: "palette\.plain"/)
+  assert.equal(zhMessages.palette.plain, "朴素默认")
+  assert.equal(enMessages.palette.plain, "Plain Default")
+})
diff --git a/web/components/palette-toggle.tsx b/web/components/palette-toggle.tsx
index 5d2db8c..4d721d2 100644
--- a/web/components/palette-toggle.tsx
+++ b/web/components/palette-toggle.tsx
@@ -1,7 +1,7 @@
 "use client"
 
 import { useEffect, useState } from "react"
-import { DropletsIcon, PaletteIcon } from "lucide-react"
+import { CircleIcon, DropletsIcon, PaletteIcon } from "lucide-react"
 
 import { useI18n } from "@/i18n/provider"
 import { Button } from "@/components/ui/button"
@@ -13,16 +13,21 @@ import {
   DropdownMenuTrigger,
 } from "@/components/ui/dropdown-menu"
 
-type PaletteMode = "blue" | "green" | "gray"
+type PaletteMode = "plain" | "blue" | "green" | "gray"
 
 const PALETTE_STORAGE_KEY = "dashboard_palette"
-const DEFAULT_PALETTE: PaletteMode = "green"
+const DEFAULT_PALETTE: PaletteMode = "plain"
 
 const paletteOptions: Array<{
   value: PaletteMode
   labelKey: string
   swatch: string
 }> = [
+  {
+    value: "plain",
+    labelKey: "palette.plain",
+    swatch: "bg-zinc-700",
+  },
   {
     value: "green",
     labelKey: "palette.green",
@@ -46,7 +51,10 @@ function readPalette(): PaletteMode {
   }
 
   const stored = window.localStorage.getItem(PALETTE_STORAGE_KEY)
-  return stored === "blue" || stored === "green" || stored === "gray"
+  return stored === "plain" ||
+    stored === "blue" ||
+    stored === "green" ||
+    stored === "gray"
     ? stored
     : DEFAULT_PALETTE
 }
@@ -68,12 +76,19 @@ export function PaletteToggle() {
 
   function handleChange(value: string) {
     const nextPalette: PaletteMode =
-      value === "blue" || value === "gray" ? value : "green"
+      value === "blue" || value === "green" || value === "gray"
+        ? value
+        : "plain"
     setPalette(nextPalette)
     applyPalette(nextPalette)
   }
 
-  const ActiveIcon = palette === "green" ? DropletsIcon : PaletteIcon
+  const ActiveIcon =
+    palette === "plain"
+      ? CircleIcon
+      : palette === "green"
+        ? DropletsIcon
+        : PaletteIcon
 
   return (
     <DropdownMenu>
diff --git a/web/messages/en-US.json b/web/messages/en-US.json
index 810241c..cede3fc 100644
--- a/web/messages/en-US.json
+++ b/web/messages/en-US.json
@@ -2364,6 +2364,7 @@
   },
   "palette": {
     "toggle": "Change accent color",
+    "plain": "Default",
     "green": "Service Green",
     "gray": "Neutral Gray",
     "blue": "Clear Blue"
diff --git a/web/messages/zh-CN.json b/web/messages/zh-CN.json
index 2076fd6..99a565b 100644
--- a/web/messages/zh-CN.json
+++ b/web/messages/zh-CN.json
@@ -2364,6 +2364,7 @@
   },
   "palette": {
     "toggle": "切换主题色",
+    "plain": "默认",
     "green": "温润服务绿",
     "gray": "中性精密灰",
     "blue": "清透科技蓝"