Not always errors. Gray (non-called POU?) and Blue (POU differs from the PLC?) text are not errors. I've also seen Red squiggly underscore. No idea what that means. I'm looking for a comprehensive list of what all these markings mean.
Where in the documentation does one find the meaning of the different POU markings that occasionally appear in the Device View? I've seen blue and red double underscore and the POU name in gray.