I've been messing around a bit with my Windows 10 theme and I noticed a difference between my installed version of Mp3tag compared to one of my portable versions that's bothering me a bit. I don't think I've made any registry changes regarding my Windows theme but that's the only explanation I can think of, that the installed versions reads something from the registry that the portable one doesn't.
Tried a clean install of 3.16 - didn't help. Portable version is 3.01. Copied some of my settings files from the portable to the installed version which also did nothing.
If it's not clear, my issue is the fact the items in the extended panel looks like they're highlighted even though they're not, and also the coloring of the header bar.
The way it looks in the portable version is consistent with how it's supposed to look and it's how all the other applications on my computer looks. If anyone has an idea about what could be the cause if this I will gladly accept it, thank you!
Tried the portable 3.16 just now and it behaves the same as the installed version. My guess then is that this is probably related to the changes you quoted as earlier version seems to work fine. Somehow the color mode doesn't jive with my theme, but it could very well be the latter that's the issue.
Turns it was a theme issue and not a Mp3tag one. The fact that 3.01 was working was tripping me up a bit, but I managed to solve it. Sorry for wasting your time.