Blair has super preppy & classy style. There's a lot of primary colors in her wardrobe. You can find a lot of boarding school-esque pieces in her closet. Her style consist of hair bows, pearls, and collared tops. Sometimes her style is really monochromatic, with neutrals, blacks, and whites. She can also be really vintage prep with her beige, lacy dresses. She also likes wearing white a lot since it is a timeless color.
Serena Style ; http://www.polyvore.com/serena_van_der_woodsens_style/collection?id=3441689
Jenny Style ; http://www.polyvore.com/cgi/collection?id=3441677