Marc Jacobs opened a new chapter for his label in roughly the time it takes to listen to a pop song. Glossy transparent shirts and dresses turned the first few models into walking holograms, their legs flashing through the see-through layers. Jacobs has never been a designer who shied away from sparkle, but here the variety and brightness of the shine made it feel new. Possibility, at least as Marc Jacobs imagines it, is not a pastel watercolor. It is a hot-pink jacket over traffic-cone tights and crystal chains, flashing under the library lights and then vanishing before you have time to process the color.