LG Ultrafine 5k -- right half is a slightly different color from left New refurbished model # 27MD5KA. I have attached a photo (apologies for the reflections). 



There is a line down the exact middle of the screen, directly below the webcam. On the right side of the screen the panel is slightly lighter than the left side (or the left is slightly darker -- I'm not sure which is the 'correct' color/brightness). You can tell very clearly in Intellij IDEA in the default darcula color scheme. It's harder to tell on light backgrounds.

I'm guessing this has something to do with the dual display port 1.2 streams that the monitor uses.

Is there any way to color correct this?

Thanks!
I've been having this issue for quite some time. Usually, a reboot would make it go away, but recently it has become much more persistent. One workaround I found was to turn on Night Shift but set it all the way to the "Less Warm" side. 

It looks like an issue with macOS. I have filed a bug report to Apple.