Marks on walls after mirror taken down

I doubt you'll be able to disguise the patches very well - it's not just dirt and dust around the pictures, the paint that was behind the pictures won't have been exposed to light all that time so won't have faded at the same rate. It's a bit like our wooded floor where the unexposed area hasn't faded.

The new buyers will probably be redecorating anyway, so I wouldn't bother painting. It's extra unnecessary work

cleaning won't help; the paint exposed to light has faded at a different rate fron the paint that was in the dark behind mirrors etc.

Don't worry about it, no need to do anything. The new owner will redecorate to their own taste anyway. Perfectly normal when people move house.

If you've sold your house and are taking things off the wall ready to pack, I really wouldn't worry about the marks and certainly wouldn't repaint anything Smintie.
Your buyers will understand.

Thank you all for your reassurance. I was just so worried about it and didn’t want the new people to be disappointed with our lovely home.

It’ll be clean and I hope they will love it too.

Marks happen from adhesive or screws clean gently with warm water mild soap or a bit of rubbing alcohol.

When we cleared my Dads house a couple years ago he had lots of paintings etc on the walls. The estate agent advised us not to decorate but to just fill in any holes from removing picture hooks.
We did that and apart from cleaning as advised by him everything else was left (needed total redecoration and new kitchen) and we still sold it within a week, for more than the asking price.

I managed to improve the marks by pouring a little talcum powder onto a soft toothbrush and applying it in little circles.
The action blurred the darker area formed by the pictures -I think by dust accumulating.
It looked better ,but I ended up repainting.
Believe me - no matter how much you clean or redecorate your buyers will have their own ideas !