For what it's worth here's some pictures taken today (overcast).
https://photos.app.goo.gl/Aycff2BE2QN2jYYi9The rear of the car is noticeably mucky but the number plate is still legible. There's dirt visible along the skirts and rear edge of the back doors. So it definitely looks like it hasn't been cleaned but it's still orange and not caked in mud.
I'm sure it would upset those who like a clean car but from a functional point if view it's fine and since it's tidy inside (ignoring the mess in the boot) I don't think anyone would think twice about it in a car park. It's just a car that hasn't been recently cleaned. In this case it was last cleaned in February 2018, about 11,000 miles ago. Which reminds me that I ought to book a service for next month
Oh and I do also wipe the rear view camera now and again, especially after rain.