By "messy" I meant -- messy to implement all the combinations (e.g. text hint on / off, read/unread/starred backgrounds...).
There is one other aspect too -- users being able to (or not being able to, more likely) -- understand the logic.
For you and @andrewilley it's different -- since that's something you *consciously* wanted and asked for (and you follow the forum, read my ramblings, etc).
But imagine some "random" user, Mr. Balthazar Quigley or Ms. Jane Smith, who goes "oh, what is account / folder labels, let me turn that off -- oh, why are my messages have some random colors"?
Let's just keep things as they are for now.
( the post-update madness is still continuing, by the way, and MS did something to Office 365 so I have to deal with that )