If you see data that you do not see immediately in MP3tag, it may be worthwhile to investigate the following:
Does your program write modifications to the files (into the tags) or does store them in an internal database?
(I mean: data like "color", "Remix", "Remixer" are no standard ID3 fields either.)
If the data is stored in an internal database only, I do not see much chance to get it out of there.
If there is a function in your program to export that data or force your program to write it to the files, then one could probably find it in the extended tags dialogue.
If the data is stored in the tags but still not visible in MP3tag, one could check in Tools>Options>Tags>Mpeg which tag versions get read, written and deleted by MP3tag.
Sometimes information is written exclusively to just one tag version (by the other program) but not read by MP3tag - and so it does not show.