NEW YORK — Giorgio Armani is keeping it light and airy for spring. His Armani Collezioni line is full of easy numbers as well as jackets, which look terrific over crisp pants or swaying skirts. At Escada, meanwhile, design director Brian Rennie loves vibrant colors and prints. He even enlisted Zandra Rhodes to create two signature patterns for the label. The results are functional pieces that are both feminine and sophisticated.