The first time Hong Kong-based photographer Romain Jacquet-Lagreze saw the color blue drench the city was not unlike falling in love. It was a warm day in summer, and as the sun set, the sky cast an azure shroud over the metropolis below. He was infatuated and intoxicated by the twinkling night—as he puts it, he had “a crush” on the light— and over the next two years he would devote summertime to chasing The Blue Moment.