Cristòbal Balenciaga did not confine himself to designing clothes in black, so the choice to limit the exhibition to black on black ought, I think, to have been explicited properly. (Or did I just miss that sign?)
That said, black is the most stylish of colours and so haute couture en noir could not possibly be anything but classy. Though the clothes displayed are accompanied by capes, hats, coiffes, jewellery and sketches, the overall impression is one of absolute sobriety.
It is not merely chic, it is the epitome of chic.