Store selected color scheme in cookies

app/controllers/preferences_controller.rb

@@ -21,6 +21,9 @@ def update
                                     else
                                       params[:user][:preferred_editor]
                                     end
+
+    cookies["_osm_color_scheme"] = params[:color_scheme]
+
     if current_user.save
       # Use a partial so that it is rendered during the next page load in the correct language.
       flash[:notice] = { :partial => "preferences/update_success_flash" }