“In the course of my work I have eliminated one color or another,” said Alberto Giacometti, “and what has remained is gray, gray, gray.” Giovanni Giacometti couldn’t have taken a more different approach. “The struggle with light is the mainspring of my work,” said the Post-Impressionist Swiss painter and father of Alberto. A new show displays more than 60 of Giovanni’s interior scenes, landscapes, and portraits of friends and family. All are watercolors, a medium well suited for catching the artist’s main muse—light. —J.V.