New York's building facades are exploding with color. A wave of large-scale murals, many commissioned by property owners and community groups, is transforming blank walls across the boroughs into a sprawling open-air gallery.

The trend has elevated once-underground artists into sought-after muralists, their work anchoring neighborhoods from the Bronx to Bushwick. The fictional artist known as Vesper has become a local star, her building-sized portraits drawing visitors who once came only for the museums.

The renaissance has also revived old debates about the line between graffiti and sanctioned art, and about who profits when a neighborhood's aesthetic becomes a draw. But on block after block, the walls tell a story the galleries can't contain.