After the latest 05.80.15 software update for my LG OLED55E7T (Australian model)...
Any device I plug in via HDMI 2.0 that is 4K (2160p) 50hz gets washed out colours.
I have a set top box that is 4k 50hz and is getting washed out colours. I have an APPLE TV that when I set it to 4k 50hz it gets washed out colours.
HDMI true deep colour is turned on.
*Interesting note, when I set my set top box to 1080i/1080p mode, the colours are normal and vibrant.
I believe this has something to do with the BT.2020 colour space compatibility. Before the software update everything was working fine.