Some weird behaviour, I hope this question is OK for this technical forum. My Google and Stackexchange/Stackoverflow searches yielded nothing. Android 8.1.0 on Nexus 6P Google phone.
All icons involving my Contacts have over time started being displayed in negative colours so that they are now pale pastel colours on a white background where I previously saw saturated colours on a black background.
It started with my Phone app only (all tabs: Favourites, Recent and Contacts) and after some weeks started happening in Messages and Contacts apps too.
Note this is not about my entire phone displaying negative colours, which can be fixed under Settings->Accessibility->Color inversion. Only my contacts default icons are affected (I don't have photos synced). Toggling the colour inversion setting doesn't fix it.
I keep my phone up to date, both app and OS updates. The changes happened over time across I think at least one or two OS (reboot) updates.
Or have these app simply decided to change the appearance of contacts icons and I'm being foolish?