I agree and have also mentioned similar before. However I do think it is more emphatic in the UK. Having said that our two daily drives are both black as we like to hide among the shoal. I prefer my AMG/MB to be a sleeper where possible. I like black as in my mind it is smart and makes me clean it (who am i kidding - get cleaned) as it shows the dirt. I do like the Subaru/Skoda vRS/Cupra colour lines developing now.
My observations, which are definitely a UK perspective -
Go on the car configuration web sites of BMW/MB/Audi/Alfa/JLR/Lexus and you will find 2-3 whites, 5+ silver/greys and 2 blacks. You may see one or just recently 2 real colours (fashion blue and a green/yellow/red?). On many of them there is often only 1 or 2 price included colours, a white and a black usually. Everything else will be an upgrade charge. What's driving this ? Value is now based on upgrades as they have a far higher profit value. Also they are pushing the "custom" colour choice schemes in several brands which have a high cost. It's all about the upsell, the Dacia advert is not too far from the truth.
As most of those cars are bought new on a PCP-lease then extras have a far higher cost on a lease for monthly charge and also tax bill. The final value of the car is costed over X years but the extras are written off over the contract which gives a higher per £ impact. So base spec is more common on these contracts.
I bought the AMG E63 Estate on an excellent MB deal but due to the lease cost of options and short lease (2Y) I added little. Black was available at 3 weeks notice all other colours were to order and 2-3 months+. At the end of the 2Y lease with all the other similar models for sale I looked to buy one as it had been great. Most of the E63's were of similar option free spec.
As "MB" is a combination of the maker and also the UK importer who builds the spec and price combinations we see this may also be involved. In the last few years MB UK have been in a battle to pass BMW in Company sales and so have run extensive incentive programs and driven stock deals. They have to order ahead for volume and choose safe colour combinations for stock to enable these. We then see them listed as stock deals on Carwow and so the motorway merges into black/silver/white in Lane 3-4. The more we drive the discount-discount-discount mentality the more this will be driven. I hate this as I like to buy 2-3 years old, fully loaded, heavily devalued, expensive cars for the daily rumbler.
I think the current trend by the larger German makers for blocky aggressive styling could look a bit daft in soft fuschia. Could you imagine a breezeblock like MB-AMG GLS in soft pale pink. I am certain there is one person out there who wants it but just may not know it yet! Having said that AMG themselves made the tonkatoy G63 in a series of mental dayglo colours. Who said Germans have no sense of humour.
https://www.guideautoweb.com/en/articles...nsive-smarties/ 
When we took a run down to Amalfi in 2017 we noticed colours look different in the sunlight there compared to the UK. The pastel colours on the Fiat 500's were so beautiful in the med sun compared to a dull UK day. Even the silver on the Coupe seemed to dance more in the sun. Black cars are less popular in hot countries due to heat absorption. Visit Dubai for the white car zone! Silver can shine and blind so is not popular in the middle east.
I also happen to think some cars look good in silver/black, but not all. We fell in love with the Coupe the second we set eyes on it. The reflections of road lights at night and buildings in the day gives a wonderful motion along the bonnet surface. The number of AeroMax built in grades of silver/granite shows that personal choice still supports this blend.
Howard the most important point I got from your email was that Aero has escaped onto the list alongside other big brands. If you can stomach the need for dealer time it will change your view forever. See if you can beg borrow or steal a good one for a week and see what happens. If you go down the Aston route a Rapide S is amazing value for age/mileage/condition right now.