Francesca Bellettini’s Plan For Kering

PARIS — White roses, white sofas, black marble tables and leather handbags. All is order and simplicity in the monochromatic boutiques that have helped propel Saint Laurent from a storied but mid-sized French designer house to one of global luxury’s superbrands.

The current outlook for luxury is far more messy, and so is the mission facing the brand’s chief executive Francesca Bellettini. After leading Saint Laurent from €550 million ($613 million) in annual sales in 2013 to €3.2…