catalina upgrade - second display colors messed up

This was the solution but silly me, I only read the response in my Mail program rather than looking at it here where you put that helpful graphic, so I didn't find an "HDR" option. Since I updated today to the latest incremental upgrade of Catalina I went to look again. Indeed, unblocking the "High Dynamic Range" box fixed the problem. Hurray! Now I don't have a large useless monitor on my desk.

Hi!

Did you try to uncheck the "HDR" option under display? That helped for me.

Apparently after the update it was check on by default.

This is my issue exactly except mine is a new 16" MBP and I was updating from the previous version of Catalina to 10.15.4 .so downgrading to Mojave isn't an option. I notice that the duplicated LG HDR 4K files have different name: one has a bunch of FFFFFs and the other is a mixture of letters and numbers. But in each case when you open the profile itself, its specifics are identical. I also noticed that starting in Safe Mode, with the shift key held down, restores the colors to where they should be. However that introduces scaling and display problems. And then when I restart normally, the color reverts to messed-up fluorescent. I had no luck with Apple Support Chat.

I have this identical problem. I just unboxed my LG-UL850 today and was shocked by how neon many of the colors looked. Going on Youtube is the equivalent of burning my retinas with all the neon oranges (should be red). I got on the phone with LG and they were about to send me a new monitor until I came across apple discussion on this problem with Catalina (which I updated last week on my 2017 MP). Glad to see this monitor isn't faulty, but hope there is a solution soon!

PS: Are you using the USB-C port for connection also? I know this is for sure an apple problem since my PS4 looked fine, but I also considered that my USB-C port could have been faulty which in turn also led to me almost returning my monitor today.

I find if I connect using the HDMI port the color goes back to normal. But that connection is not as fast as the USB-C connection and there is considerable lag just dragging the cursor across the screen. The colors also temporarily go back to normal if you start your mac in "Safe Mode," but revert to neon when you start normally.