Seems to be greyish. I ran a Google picture search for “police nationale du Tchad”, and there’s a lot of photos of people wearing Chadian police uniforms. But I’ve never been there either.
The Broward County Sheriff’s office (think Ft. Lauderdale Florida) also equips their bicycle officers with bright yellow polo shirts with embroidered chest badge & shoulder patches. The color scheme for their cars is white and dark green and the general duty uniform is a similar dark green. The polo shirts are actually green on the bottom half and yellow on the top half.
The other day I was in the airport in Mexico City. The airport police wore black trousers, a white shirt, and a bright orange hat. The usual Latin American high-peaked army/police style billed hat, but the cover was that neon dayglow orange.
Here’s an example of the color, if not the same shape hat I saw:
It’s not the base color, but the Italian Polizia stradale (traffic police) uniforms have a wide purple stripe down each leg. I have never noticed that before, but it has a lighter colored line in the middle, so maybe it is meant to look like a road?
In North Korea at least one of the traffic police uniforms is a white shirt, jacket, hat and socks, with medium blue trousers or skirt and some green detailing. Pretty fetching actually.
They are a legit guard unit though. Perhaps not police but despite their flamboyant uniforms they are real guards and good ones at that. Don’t mess with them thinking they are just there for show. Maybe they will not arrest you but they will kick your ass if need be.
The army uniforms, to be precise.
A bigger picture shows what seem to be standard lampassen – two broad stripes, with the fabric of the trousers showing between them.
Evidently some state police in Mexico use a shade of violet.
But that’s not red, purple or yellow…which is what the OP was asking about.
(except for tiny flags or badges on the uniforms, which probably doesn’t count)
Take a look again
A quick search found a few.
Albania (source)
Sri Lanka mounted police (ceremonial dress) (source)
https://www.police.lk/images/mounted_police/2018/uniform/uniforms-1.gif
Pamplona, Spain. (not sure if this is regional or national) (source)
Turkey (source)
And Australian police in a once-per-year event.
When the show “True Stories of the Highway Patrol” was on back in the 90’s I could swear I remember them wearing an olive drab uniform jacket.
Then there is white. I have seen officers in the Caribbean wearing white. Around here the rank of Lieutenant and above wore white uniform shirts with the same color trousers as regular officers. That trend has been faded out over the past decade.
This is the History page from the California Highway Patrol. Historically their uniforms were tan pants with a blue and gold side stripe and an olive drab shirt/jacket. At least some of their uniforms are still those colors today.
It says “policía foral” on the uniforms, which indicates it’s regional. The term foro in Spain refers to the autonomous communities, which are regions with far-reaching self-administrative autonomy.