It seems an issue with the monitor profile.
However, I would suggest you to first update Lightroom to the latest version 6.5, click Help>Updates.
Also please check the following link for the monitor profile: How do I change my monitor profile to check whether it’s corrupted?
Let me know if it helps.
thank you for your help , i tried this before and it didn`t work
but i found a solution here
**delete the Previews.lrdata of the catalog.
Thank you for the update, glad to know it is working for you.