I don't find the headline graph that convincing. Firstly, it's only based on items in this museum's collection, which is quite a biased set as it says in the article.
Secondly - if you actually look at the colour chart closely, you can see that although there is a trend of more grayscale objects in the collection, within the coloured section there's also a trend away from almost everything being some shade of yellow, orange or brown towards a much broader range of hues. Blues, greens and purples seem much better represented.
It looks to me like ~70% of the colours were basically "brown" in the 1800s, and now ~40% are white/gray/black. Seems more a reflection of modern objects being made more out of metal and plastic and less out of wood than anything else. Again, this is putting aside the clear bias in the samples here.
I'm sure there are trends going on (and the car colour one seems legit to me) but I think this overblows it a little. Fashion ebbs and flows.