I did a screen capture on Windows 10, saved it as PNG, then inserted it into Writer. It appears quite gray. What could cause this? I will try to use the “Upload” icon to attach the images showing how different they are.
In response to a comment, below is the PNG that goes gray when inserted into Impress. Oddly, I can’t seem to cause the picture to turn gray again when inserting because I just tried it now before uploading.
Can you post the png that turns grey on insert into LO? Use the up pointing arrow icon to upload.
I can’t see a problem with the image file. Might have been another process using too many resources.
OK, thanks. Did you want to propose that as a possible answer? It might help others who see this to realize that it is just a matter of trying again.
Nah. There isn’t really an answer unless it was last week and Windows was waiting for a reboot to complete the installation of updates. That always causes weirdness.
Possibly (if you still have it) uploading your original (part of) document with the gray image in it could already help understand what is causing that.
No, I’ve done a gazillion saves since then. 
The evidence is gone!