This seems to be an issue due to graphics.
Would suggest you to go to Lightroom Preferences > Performance > uncheck "use graphics processor" and restart Lightroom and check again.
thank you for this fast proposition. I did so and it works again, the first problem.
But the second still remains. Even in the "organisation strip" for clipping the video's colors ar correct, but the display of the large image stays green.....?
Thanks for the update.
Can you please check if the same happens for newly imported images or if the same happens in a new catalog.
Yes I can, but not before wednesday. Afterwards I will inform you.