I think many people who park in red zones do it thinking it’s no big deal..that they’re people who observe the law when it suits them (which they do, most of the time).
I think maybe making them feel not like a #******# but as someone not to be trusted might get the point across better.
In the City of LA it’s against the law to use gas powered leaf blowers.
Many people don’t care. Responses vary from plain ‘I don’t care’ to but they work so hard and it’s only a hour a week’ to ‘I’m sure they don’t know about the law’.
New neighbor moved in and I heard all the same answers.
I explained that the law has been on the books for years and the gardeners rely on the homeowners lack of knowledge to continue to use the blowers. I also explained that if they used electric powered ones they could plug into the house current which would also save them the money for the fuel and oil which is used in the gas ones. I pointed out that the blowers throw a lot of very fine particulates into the air which can cause major problems for people with breathing concerns, but also especially for children.
I’ve learned to add the final touch: “Since they know it’s against the law but they continue to do it and break the law, how can you be sure they won’t break other laws which could include theft from your property?”
That one stopped her. She said they had used the gardener because he was cheap and it was for a limited time only.

My point is that rather than focus on inciting ‘good’ behavior, focus on the bad.

Maybe have a flyer which states that there is an active neighborhood watch and one of the things that residents monitor is cars parked in wrong areas. Cars parked in wrong areas have been involved in many later reported acts of criminal behavior.
In other words, parking in a red zone is suspicious behavior and may be reported not because it’s a red zone but because the person doing it could be a criminal.
I don’t know if it would change some people’s behavior but maybe being considered a possible criminal might make people think twice about it. Everyone hates parking laws (the ‘divine’ right of the driver) but to be thought to possibly be a dealer, etc…
Up parking in red zones from ‘parking tard’ to ‘suspicious behavior’.
Maybe add that the license plate number has been recorded. Then maybe something short about Neighborhood Watch programs and if the driver is interested for their area they can contact their local police/sheriff’s department. Now you’re not just nosey neighbors, you’re part of a greater civic minded movement….

I’ve adopted a more PC label for these jerks: Mentally Incaparkitated.