how do they do the black?
I'm guessing these are just technically uninformed renders with no basis in actually-proposed applications, but it seems at least plausible that one could combine transparent OLED with a transparent LCD backing (sort of the inversion of a backlight) to create a variable-transparency screen.
But while I've never seen it, I don't see why you couldn't put a transparent OLED over an LCD screen like the one in your laptop. Combined, I think they'd give you every combination of color and opacity you could want.
I don't know if there's any technology that combines the two capabilities into a single layer.