@Hangman@Lee D thank you so much for you replies!
Opening the photos in other photo viewers there is no colour change. I have this phenomenon only in Affinity.
So the monitor settings should be fine, I guess.
The photos have the colour profile eciRGB, I checked it again. Does this information help?
Maybe I have to install this colour profile in Affinity? How does that work?
And it seems that it's more or less heavy. At the moment it seems not as best at it already was before. So I'm acutally a bit confused.
I'm sending you a screenshot from a current unfortunately very mild example but I hope you still can see the issue I notice.
On the left: Windows Photo Preview
On the right: Affinity Photo 2
I will see to send you the original photo too.
Thank you very much !