https://forums.d2jsp.org/topic.php?t=92284726&f=34&o=0 Thread from another user where I helped "fix" the issue.

But there's an underlying problem. When screenshots aren't pasted into paint they are high contrast.
Google only turns up RGB color settings issues across different programs.
But what is the issue causing these dark screenshots in general? Would be nice to know for future reference.

Does the same thing happen with the snip tool? Win+shift+S

How does changing the ingame brightness affect the screenshots?

My guess would be something funky happening in the graphics driver control panel; more specifcally the colour and gamma profiles.

I didn’t get more info other than me telling him to paste it into paint and it fixed the darkness but was still a little off color wise.
I think it has something to do with him using windows key+print screen and it showing that short dark screen to confirm it happened.
I don’t think I will be able to solve this other than the quick fix I got for him but I appreciate you trying to help.
This was 2weeks ago and he hasn’t said anything else so I assume he fixed it.