Beginning with the “Fiesta” dress from his debut collection, in 1959, the couturier Valentino Garavani, 93, used the color red in every single collection he designed through 2008, when he retired. That color—not orangey, not pinkish, but pure cochineal—is the subject of “Horizons/Red,” the inaugural show at the exhibition space, PM23. The new venue hosts cultural initiatives supported by the Fondazione Valentino Garavani e Giancarlo Giammetti, and opened last month in a former Vatican school on Rome’s Piazza Mignanelli. Fifty of Valentino’s red designs are on show alongside 30 works by artists, among them, Francis Bacon, Gerhard Richter, Helen Frankenthaler, and Lucio Fontana. —Jessica Iredale