It only just started? I noticed the green tint on mine pretty early after i got it. I like to swipe my phone before going to bed. So, dark mode and low brightness will show the green tint very easily. It's a common issue for the whole Sense 8 series. It's also slightly noticeable on my R8s Pro. Bit of a glow along the edges.
There is an option in a Troubleshooting menu that will lower the level of green tintedness. And if your device is still on warranty, i heard they will exchange to Sense 9 for you. I kept mine because i wanted the "Made In Japan" phone.