This is the first time I have seen this in MSFS.  Reminds me of the discrepancy along state lines with Megascenery Earth in FSX, where neighboring states were processed into scenery on different dates.  This is flying \west to east over central Illinios today.  This MSFS discrepancy was from horizon to horizon.  No clue what is going on here.  Took time in flight to empty my cache and allow it to rebuild.  Made no difference.  Anyone have an answer?

 

You are lucky if this is the first time you have seen this discrepancy between the colours of tiles. I have seen it every sim where I used photo scenery which includes MSFS scenery many times all over the world. It pretty common place.

I've seen this often as well including in my X-plane install using ortho4xp. If you check the same area in Bing maps you will likely see the same anomaly. The areas each side of the line have imagery from different dates, sometimes even different seasons or years. Pretty hard to avoid with ortho photos, but hopefully one day they can develop some AI to blend all of the orthophotos into more consistent and realistic colors. That would hopefully get rid of those pervasive green roads and overly green textures that we see so often in the sim.

If I had to guess I'd say it's down to Bing Maps imagery and has nothing to do with the sim as such. It's just images taken at a different time. There's quite a few such anomalies in Illinois.