I believe this was tried somewhere in California, too

Menlo Park, green blazers, I believe. I recall a 99% Invisible episode about them.

I'm only 42.... police in the UK got their perpetual guns and SWAT outfits post 'war on terror' iirc. I remember clearly seeing the first 'bobby on the beat' in my home town wearing a stab vest over his white shirt and tie. He had traditional dark blue trousers and shoes (rather than combat boots). It is a rural town. I never heard of a knife crime. We thought it was health and safety nonsense. This would be mid 2000s.

I told a policemen friend (non uniform) that i didn't like that they moved someone after to black polo shirts. He said it was because sweat made the colour run from the stab vests into their white shirts...