Nearly 100% of time while walking down on the farm there are green flashes at the bottom edge of the screen mostly (sometimes to the right as well). It does not happen when walking left, right, or up. I think I first noticed it in summer year 1, and I am now on Year 1 Winter 22.
I have also noticed it in random places in town but was only able to reproduce it while standing on the bridge near Dippa’s (i think) house just north of the taco truck. The flashing happens when standing still on the bridge, or going down. The flashing occurs in the plants lining the river, the stairs toward the temple (upper right) and in the plants behind the school (lower left).
I’m playing in the X box series X through game pass (build version 1.0-946).