I just tested this area. I also get the darker green populating in about 800 to 1000 ft AGL. Over 2000 feet they start to go back into the “normal” green terrain (screen capture in game 2K monitor).
Also, the purple… those I get too when approaching the hills (screen capture from video 1K).
I’ve actually never experienced this before. Weird how it pulls in/out those dark green tiles and the purple for the hills.