I have a project with a lower third and a book mockup with some keyframed opacity and some shadows, which I've used multiple times. I've never had any issues with this setup until I recently changed the comp background colour to make it easier to see what I was working on.
I'm under the impression that this background colour should not be visible in the final render, but any part of the lower third that has partial opacity (not 0 or 100%) will be changed to the background colour, still with opacity applied. So a grey/black shadow or fade will appear green if the background colour is set to green, and as an asset fades up, it will go from darker to brighter.
This colour change is not visible in the composition window but is visible in Quicktime and when imported into Premiere Pro or After Effects.
I've tried exporting from both After Effects 22.6.5 and 24.1.0
The Render settings I have tried are:
Field render: Off/Upper Field
All other settings are default for "Best settings"
The Output Module settings I have tried:
Quicktime Apple ProRes 4444
RGB + Alpha
I have also tried exporting as PNG, TIFF and Quicktime Uncompressed RGB 8-bit it does not show the background colour, as expected. Is this an issue with the ProRes 4444 codec or something else?
Also note in the second screenshot, the red border is visible in quicktime but not in PP or AE.