diff --git a/src/components/WindowTitle.tsx b/src/components/WindowTitle.tsx
index bae059d1..113cfea9 100644
--- a/src/components/WindowTitle.tsx
+++ b/src/components/WindowTitle.tsx
@@ -3,6 +3,7 @@ import { WindowInstance } from "@/types/app";
 import { WindowToolbar } from "./WindowToolbar";
 import { WindowRenderer } from "./WindowRenderer";
 import { useDynamicWindowTitle } from "./DynamicWindowTitle";
+import { useGrimoire } from "@/core/state";
 
 interface WindowTileProps {
   id: string;
@@ -13,12 +14,20 @@ interface WindowTileProps {
 
 export function WindowTile({ id, window, path, onClose }: WindowTileProps) {
   const { title, icon, tooltip } = useDynamicWindowTitle(window);
+  const { setWindowBackgroundColor } = useGrimoire();
   const Icon = icon;
 
   // Custom toolbar renderer to include icon
   const renderToolbar = () => {
     return (
-      <div className="mosaic-window-toolbar draggable flex items-center justify-between w-full">
+      <div
+        className="mosaic-window-toolbar draggable flex items-center justify-between w-full transition-colors"
+        style={
+          window.backgroundColor
+            ? { backgroundColor: window.backgroundColor + "30" }
+            : undefined
+        }
+      >
         <div className="mosaic-window-title flex items-center gap-2 flex-1">
           {Icon && (
             <span title={tooltip} className="flex-shrink-0">
@@ -29,7 +38,13 @@ export function WindowTile({ id, window, path, onClose }: WindowTileProps) {
             {title}
           </span>
         </div>
-        <WindowToolbar onClose={() => onClose(id)} />
+        <WindowToolbar
+          onClose={() => onClose(id)}
+          backgroundColor={window.backgroundColor}
+          onBackgroundColorChange={(color) =>
+            setWindowBackgroundColor(id, color)
+          }
+        />
       </div>
     );
   };
diff --git a/src/components/WindowToolbar.tsx b/src/components/WindowToolbar.tsx
index 05cbf0ce..396a1ec0 100644
--- a/src/components/WindowToolbar.tsx
+++ b/src/components/WindowToolbar.tsx
@@ -1,12 +1,76 @@
-import { X } from "lucide-react";
+import { X, Palette } from "lucide-react";
+import { useState } from "react";
 
 interface WindowToolbarProps {
   onClose?: () => void;
+  backgroundColor?: string;
+  onBackgroundColorChange?: (color: string) => void;
 }
 
-export function WindowToolbar({ onClose }: WindowToolbarProps) {
+const COLORS = [
+  { label: "Default", value: undefined },
+  { label: "Red", value: "#ef4444" },
+  { label: "Orange", value: "#f97316" },
+  { label: "Yellow", value: "#eab308" },
+  { label: "Green", value: "#22c55e" },
+  { label: "Cyan", value: "#06b6d4" },
+  { label: "Blue", value: "#3b82f6" },
+  { label: "Purple", value: "#8b5cf6" },
+  { label: "Pink", value: "#ec4899" },
+  { label: "Indigo", value: "#6366f1" },
+  { label: "Teal", value: "#14b8a6" },
+  { label: "Gray", value: "#6b7280" },
+];
+
+export function WindowToolbar({
+  onClose,
+  backgroundColor,
+  onBackgroundColorChange,
+}: WindowToolbarProps) {
+  const [showColorPicker, setShowColorPicker] = useState(false);
+
   return (
-    <>
+    <div className="flex items-center gap-1">
+      <div className="relative">
+        <button
+          className="p-1 rounded text-muted-foreground hover:text-foreground hover:bg-muted/50 transition-colors"
+          onClick={() => setShowColorPicker(!showColorPicker)}
+          title="Change window color"
+        >
+          <Palette className="size-4" />
+        </button>
+
+        {showColorPicker && (
+          <div className="absolute right-0 top-full mt-2 bg-background border border-border rounded-lg shadow-lg p-3 z-50">
+            <div className="grid grid-cols-4 gap-3">
+              {COLORS.map((color) => (
+                <button
+                  key={color.value || "default"}
+                  className="w-8 h-8 rounded border-2 flex items-center justify-center flex-shrink-0 hover:scale-110 transition-transform"
+                  style={{
+                    backgroundColor: color.value || "transparent",
+                    borderColor:
+                      backgroundColor === color.value ? "#fff" : "#ccc",
+                    borderStyle: !color.value ? "dashed" : "solid",
+                  }}
+                  onClick={() => {
+                    onBackgroundColorChange?.(color.value || "");
+                    setShowColorPicker(false);
+                  }}
+                  title={color.label}
+                >
+                  {!color.value && (
+                    <span className="text-xs font-bold text-muted-foreground">
+                      ×
+                    </span>
+                  )}
+                </button>
+              ))}
+            </div>
+          </div>
+        )}
+      </div>
+
       {onClose && (
         <button
           className="p-1 rounded text-muted-foreground hover:text-foreground hover:bg-muted/50 transition-colors"
@@ -16,6 +80,6 @@ export function WindowToolbar({ onClose }: WindowToolbarProps) {
           <X className="size-4" />
         </button>
       )}
-    </>
+    </div>
   );
 }
diff --git a/src/core/logic.ts b/src/core/logic.ts
index 51d08bde..e9541793 100644
--- a/src/core/logic.ts
+++ b/src/core/logic.ts
@@ -263,3 +263,28 @@ export const setActiveAccountRelays = (
     },
   };
 };
+
+/**
+ * Updates the background color of a window.
+ */
+export const setWindowBackgroundColor = (
+  state: GrimoireState,
+  windowId: string,
+  backgroundColor: string,
+): GrimoireState => {
+  const window = state.windows[windowId];
+  if (!window) {
+    return state;
+  }
+
+  return {
+    ...state,
+    windows: {
+      ...state.windows,
+      [windowId]: {
+        ...window,
+        backgroundColor,
+      },
+    },
+  };
+};
diff --git a/src/core/state.ts b/src/core/state.ts
index 55fff118..eca0384e 100644
--- a/src/core/state.ts
+++ b/src/core/state.ts
@@ -104,5 +104,9 @@ export const useGrimoire = () => {
       setState((prev) => Logic.setActiveAccount(prev, pubkey)),
     setActiveAccountRelays: (relays: any) =>
       setState((prev) => Logic.setActiveAccountRelays(prev, relays)),
+    setWindowBackgroundColor: (windowId: string, backgroundColor: string) =>
+      setState((prev) =>
+        Logic.setWindowBackgroundColor(prev, windowId, backgroundColor),
+      ),
   };
 };
diff --git a/src/types/app.ts b/src/types/app.ts
index 73c13da3..a10291c2 100644
--- a/src/types/app.ts
+++ b/src/types/app.ts
@@ -24,6 +24,7 @@ export interface WindowInstance {
   appId: AppId;
   title: string;
   props: any;
+  backgroundColor?: string;
 }
 
 export interface Workspace {