Update demo/app.py

stone as natural hue

demo/app.py

@@ -12,7 +12,7 @@ ROOT       = Path(__file__).parent
 CSS_STRING = (ROOT / "css.css").read_text(encoding="utf8")
 
 # ── 2.  Theme (orange primary, light-first) ──────────────────────
-THEME = gr.themes.Ocean(primary_hue="indigo", secondary_hue="violet", neutral_hue="emerald").set(
+THEME = gr.themes.Ocean(primary_hue="indigo", secondary_hue="violet", neutral_hue="stone").set(
     background_fill_primary="*primary_100"
 )