Some Huawei Mate 20 Pro owners have been complaining about the display of their brand-new flagship device. A green hue has been seen on faulty handsets, to the extent that it becomes quite visible under certain conditions. The cause of the verdant tint has yet to be fully explained; affected consumers have been offered replacements in some countries.
https://www.notebookcheck.net/Green-hue-affecting-faulty-Huawei-Mate-20-Pro-devices.355611.0.html
In all markets? As recent as yesterday not all EU countries would accept exchanges due to faulty screens.
Not only that, but in Romania for example they didn't even acknowledge it as an issue. They say that it's normal for a curved screen. Although I do own a Samsung S9 plus that does not have any green tint issue whatsoever.
Most of LG panel has this issues, Check you panel if it is BOE, keep the phone, if it is LG, well, give it back to Huawei to get replacement, until you get a BOE version, BOE panel is the top one with no any issues.