Note that in the OPs photo (https://imgur.com/a/SCHGo4N) it happens to every other image consistently. If you were shooting raw (with Pixel, not familiar with Xiaomi camera), it would save the raw and jpeg together. The gallery not being able to display the raw image results in the green image would be consistent with whats being shown.

FWIW the redmi note 8 pro main 64mp camera (it's a Samsung sensor shared by many phones) can shoot in raw but only with a gcam port, not with the default Xiaomi camera app.

Making a guess here, the envelope has a distinct shade of pink, which may trigger some processing. It looks like it is in "AI" mode, and who knows what "AI" does.