jonathan18: We’ve got silver/black plates on both our cars and based on my observations is it’s the reflectivity of the ‘black’ background that causes the (in)visibility issue - the background isn’t a true black but has a distinctly reflective ‘texture’ that looks silver under headlights (and on some angles with direct sunlight). Ironically, if they’d just left the background black I imagine they’d have been fine!

But then they wouldn't have a nice large reflective target for the speed laser that you are legally required to attach to your car.