When, as a young man, Hubert de Givenchy was invited to grand dances, he sat out because he didn’t dance. He has said he spent the time “looking.” There was much to catch his eye. The newly optimistic mood in Paris that followed the Liberation in the late 1940s heralded a flurry of balls, tactfully held in aid of war charities. Vogue Paris published in color the Bal des Oiseaux at the Pal…