I have a PWA and it used to have a garish theme color but then I set it to something more muted in manifest.json... but it's still showing up garish!
I've searched my whole codebase for the offending color (#9600ff) and haven't found it anywhere. I thought it was a caching thing but then I tried it on new devices that had never loaded the page and had the same issue.
The clue was when it showed the new color while offline as a PWA, but not once it went online.
Eventually realized I had changed it in the manifest but NOT changed it in a different place:
<meta name='theme-color' content="#9600FF">
........my searching thus far had been case-sensitive. I wrote this Q with its A at the same time because I had tried searching for this and didn't find answers and spent an hour frustratedly investigating.