If Manu Tab in PFCG is showing Red color means no menu item has been define.
Manu in PFCG is usually helpful when User are allowed to use certain trasaction code as oppose to SAP Menu.
If you change the settings from SAP menu to User manu then user can only view those tcode which is assign in Menu (Provided this role is assign to that user).
Hope this will help.
-Pinkle
