Amazon launched four new Kindles this week, maybe the biggest single launch day in the 17-year history of the company’s wildly successful e-reader. One of them even comes in color! It is very much not a coincidence that the launch happened roughly a year after Panos Panay joined the company. Panay, a longtime Microsoft executive who was for years in charge of all things Windows and Surface, is now leading the devices and services team at Amazon. His big task is Alexa...