Once reserved for the home and gym, sweatshirts have taken a well-heeled turn. Designers such as Kenzo, Ostwald Helgason and Preen showcase artful graphics in fun colors, while Sophie Hulme and 3.1 Phillip Lim work a more sophisticated angle with tailored versions in classic crisp tones. We are reaching the end of May, but the weather can still be cool, perfect for layering the coziest outerwear of the season.