Rarity (White, Blue, Purple, Green)

So, based on what I've observed in the game and the forums, this seems to be the order of rarity from most common to ultra-rare.

That being the case, I am curious about three things:

1. Why does rarity change in the Town Hall?
Town Upgrades stay the same from day to day – there's always the same list of fountains, statues, light posts, seating, and decor. However, today they are all labeled in white. Yesterday, for example, one of the Buddhas was blue and one was purple. Tomorrow, who knows?

2. Is there a benefit associated with rarity?
Does a purple upgrade give more town happiness than a white one? Does my mayor get nicer rewards wearing rarer clothing? Is there a difference in quests if she has a larger house with rare furniture, walls, and flooring? Or do I just get warm fuzzies from having the rarest or the best?

3. What's with the glasses-related sexism?
Rarity in the Clothes Boutique seems otherwise evenly distributed between male and female: there's an equal or roughly-equal number of male and female outfits in each category, and so far I haven't seen anything but white-label shoes for both. But I haven't seen a single set of women's glasses that weren't white-label, while about half of the men's I've seen have been blue or purple. If the answer to #2 is "yes," that seems like a distressing bit of misogyny. (And even if it's not... why the disparity?)

1. The rarity changing in the Town Hall is a minor visual oopsie that usually results from checking out the town upgrades after looking through the items in the General Store. There is no rarity assigned to Town Upgrades, so feel free to ignore that. It's currently being worked on.

2. Yes (with the exception of the town upgrades, since they don't have any rarity), but we're keeping the mystery to let our players figure it out

3. There are rarities with clothing, but what you might be seeing is simply that you're currently a little unlucky with the random selection, and that will change, eventually.

I haven't seen any green labeled items. Do they only show up with the mysterious visitor?

Keep playing, you'll discover them eventually. (The actual answer to your question is "maybe, maybe not" which I suppose isn't what you were looking for.)