Please follow the below steps.
> Launch Lightroom
> Click on Edit > Preferences(in Windows)
Lightroom > Preferences(in Mac)
> Click on Performance Tab
> Uncheck Use Display Processor
> Click on OK
> Quit Lightroom
> Relaunch Lightroom and check for the issue.
Let me know if this helps.
If that does not work, you might need to recalibrate your monitor due to the profile file becoming corrupted.
Thanks. Mrinmay's suggestion fixed it. SP
This fixed it - thanks very much Mrinmay! SP