It's almost refreshing in a way. Can you imagine what present day marketeers would make of the dial colour? We'd have paragraphs of florid prose, whereas the attitude in the 70s seemed to be more along the lines of "yeah, it's brown".

I don't know why it wasn't simply translated as "smoke", though, it seems more apt than than charcoal.

Three very different finishes to the dial is the key, even though they all get described as "luminous charcoal" in the brochures, rather unhelpfully.

The Silverstone's dial is what Heuer normally means when they describe a dial as "luminous", i.e. a radially brushed "starburst" finish emanating from the centre of the dial.

The Daytona dial is pretty unique (apart from its blue brother of course), with what appears to be an increasing amount of pigment as you get closer to the edge of the dial. For me, it's the Daytona dial where the name "fumé" makes most sense because it really does look smoked.

The Carrera's dial has a "Côte de Geneves" finish (i.e. "Coast of Geneva") - I believe the name is supposed to evoke waves lapping on the shore of Lake Geneva, and that description really works (though you might hope the water of Lake Geneva is closer to the blue dial than the brown one!). It's a really three-dimensional dial and the play of light over it is fascinating.

So all different, all interesting and all probably overdue a renaissance now that chocolate dials seem to be experiencing more popularity of late, I agree.