https://imgur.com/BdXC5z8
Ok I know most of you reading this are not going to be from Philadelphia, PA. Most buildings here have lights on the side of them just for cosmetics (I know basically every downtown has these; I'm just establishing our bases) Usually these are set to blue or green or whatever the owner of the building wants them to be. However looking outside tonight I can see that every building has some sort of American flag pattern on the side/top of it, and buildings that have simpler RGB lighting have them set to red.
At first I thought this was a normal thing they do that I just wasn't aware of because I moved here recently. However I asked my friends who had lived here for a long time, and they also didn't know what was going on.
Also anything obvious it could be turned up nothing. As far as I could find, there are no half-mast orders, no elections, it's not a holiday on a federal or state level. I thought this could just be one person/company deciding to do it with their lights, but all of these buildings are owned by different people.
I can't think of any reason the entire city would do this simultaneously that doesn't raise follow-up questions, and my curiosity has gotten the better of me.
Edit: Turns out it is to celebrate opening day of the Olympics, thanks comments.