Update/winkel (#5597)

* Winkel: Update theme colors.

* Winkel: Update theme screenshot.

winkel/theme.json

@@ -5,9 +5,9 @@
             "palette": [
                 {
                     "slug": "primary",
-                    "color": "#444444",
+                    "color": "#676767",
                     "name": "Primary",
-                    "default": "#444444"
+                    "default": "#676767"
                 },
                 {
                     "slug": "foreground",