Sonia Rykiel's muse is a sexy businesswoman who knows ... narrow black pants and pencil skirts, fluffy fur vests and minis, and sheer knits hit on most of fall's major trends.

With her dramatic smoky-eyed, flame-haired looks, the bookish designer Sonia Rykiel was like a latter-day Colette, Sarah Bernhardt, and Marchesa Casati rolled into one—and as powerful ...