My Note 9, just went past it's 1 year warranty, and developed a green tint in low brightness (Under about 35%) mostly noticable in grey areas. The display was fine until suddenly this morning when I turned the phone on it was green tinted. I use the phone mostly indoors so I need to use the phone in low brightnesses.
A quick Google search told me this is a common issue in Samsung high end phones. I have never updated my phone since I bought it, and I haven't recently installed anything new either. I have tried: deleting cache partition, soft reset, safe mode, factory reset. None of it worked.
