to highlight the fact that it isn't
I like this suggestion.
I have a Smart Playlist set up in iTunes to do just this - but it would be great if it could be highlighted in MP3Tag (you know, before it gets imported into iTunes or a n other player...).
so are we talking about missing information or the wrong genre ?
To me, we're just talking about Genres that are NOT in your action list for setting Genre. OR no Genre set.
May colour A if not a standard Genre and colour B if not in your user-defined genres. I think "no genre" would be better under a more generic "Colour field if missing" that could apply to any fields in the Tag Panel...
I would like to add that the colours would have to be chosen wisely as using another background than white would most likely reduce the contrast and make it harder to read for people with eye problems.
And depending on the colours a coloured background could render the contents unreadable for people with red-green colour blindness.
Obvs you should be able to pick colours that you work for you.
PS. I did have a user contact me saying their software had stopped working and I found someone had configured white text on a white background