Serato caches the file information for each song in its own database, so each time you open the program it doesn't have to request that information from each individual track. Rescanning simply goes through each track's file, reads the ID3, and then updates the Serato library accordingly. If you make changes in something like iTunes, it'll automatically pull in that info when the tags are rescanned.

The filename is simply the name of the actual file itself, so that won't change if you rescan it. The colors will also remain intact.

To test, just drag a few of your files onto the Rescan button, and Serato will only rescan the tags for those tracks.

In short.. rescanning the tags does not change any part of your tags. It simply reminds SSL of what info is in the tags.

i've been adding info such as #top40 #house etc in the Genre field in my smart crates in Serato DJ 1.9.10 on my Macbook Pro 2017, and each time I re scan SOME files, the genre changes back to its original tag info.