I've reset PRAM, NVRAM, and SMC to no avail. Turning True Tone on and off doesn't do anything either.
The rainbow flashing returns no matter what I do.
MacBook Pro 13″, macOS 10.15
Check if you have same issue in safe mode, then you can Contact Apple Support.
Note: Safe mode prevents your Mac from loading certain software as it starts up, including login items, system extensions not required by macOS, and fonts not installed by macOS. It also does a basic check of your startup disk, similar to using First Aid in Disk Utility. And it deletes some system caches, including font caches and the kernel cache, which are automatically created again as needed.
Check if you have same issue in safe mode, then you can Contact Apple Support.
Note: Safe mode prevents your Mac from loading certain software as it starts up, including login items, system extensions not required by macOS, and fonts not installed by macOS. It also does a basic check of your startup disk, similar to using First Aid in Disk Utility. And it deletes some system caches, including font caches and the kernel cache, which are automatically created again as needed.
Once you choose Shutdown, you are not expecting your Mac to do anything more for you.
Any wacky things that appear on the screen are of no importance whatsoever. They are far more indicative of some sloppy programming than any sort of problem with your Mac.
Foregtaboutit.
MacBook Pro 13" 2020 flashing rainbow colors when shutting down, less than 2 weeks old
