It's possible that you have a bad monitor profile. See if there is an updated driver for your monitor. You can also try switching to a standard sRGB profile and see if that solves the problem.
This seems to be an issue due to graphics processor.
Go to Lightroom Preferences > Performance > uncheck use graphics processor
I have only had the monitor for about a month - Lonovo LI2821
I will try these things!
Really? I didn't think of that one.
OK turning the graphics processor off seemed to fix that problem...... BUT does that mean something is wrong with my processor?
I believe the color difference in Library and develop module could be either due to bad monitor profile as you mentioned or it could be due to incompatible graphics card processor.
JIm is right, you have a defective monitor profile, probably caused by a Windows 10 update.
Try setting the monitor profile to sRGB as described here: http://www.lightroomqueen.com/articles-page/how-do-i-change-my-monitor-profile-to-check-wh ether-its-corrupted/
If that fixes the issue, you should ideally calibrate your monitor with a hardware calibrator.
No, I don't believe so. A graphics processor feature is primarily helping users who have the new high-resolution monitors. The feature seems to be causing a lot of problems for other users. In reality, unless you have one of the high resolution monitors, it is unlikely that you will see any real benefit from using the graphics processor even if it is compatible with Lightroom. Just leave it unchecked and don't worry about it.
It's the first time I've seen that turning off the gpu fixes this problem, but I won't rule out that it did.
But you have the typical yellowish brown histogram, which is a telltale sign of a broken monitor profile.
So I think you should try setting the monitor profile to sRGB, turn the gpu back on, and then calibrate if it fixes the issue.
My money would be on the monitor profile too, but in reality they're different manifestations of the same underlying problem: The display color management chain is failing.
One thing that can happen with a bad profile is that a conversion from, say, Adobe RGB works fine (Library), but a conversion from linear ProPhoto can fail (Develop). Or vice versa.
With GPU on, the display profile conversion is performed by the GPU, while in the off state it's shifted back to the CPU. It can very well happen that a bad profile causes the GPU-resident color management to trip - but the CPU resident CM handles the profile correctly.
IOW the underlying problem is the display profile in both cases, but turning GPU off conceals it. Try sRGB as per Per's post #7.
Thanks for that explanation Dag, which makes it easier to understand what's going on.
Although turning the gpu off hides the problem, this is a situation where I wouldn't have peace of mind until I knew that the profile was sound, which means calibrating, or at least replacing the profile with sRGB.
Absolutely. I recalibrate at the slightest suspicion that something may be fractionally off.
Still, it should be noted that GPU color management is notoriously unreliable, probably through no fault of Adobe (this is all in the OpenGL engine). In Photoshop, a persistent and well-known bug causes color banding with ProPhoto files, and may cause black clipping in any color space. So I always keep it off there.