Even with just a T-shirt and sneakers, a pair will make your outfit seem infinitely more special than denim would. Silky shorts feel like you're wearing pajamas, too, so you can enjoy the look all weekend without sacrificing lounge-around comfort.
Rather than wear your colorful shorts with a neutral top, pick a shirt in a slightly darker or lighter shade of the same hue. Suddenly what could've looked like a soccer mom outfit will turn into a bonafide look.
Mixing opposite styles is a fast way to pull an ensemble out of ho-hum territory. One of the easiest ways to do this is with sneakers and a ladylike dress, but once you've got that down don't be scared to experiment! Some ideas to get you started: pair a baseball T-shirt with a lace skirt or look for sporty board-shorts in a floral print.
If you wear just one piece in a bold eye-catching print, it should be statement enough to carry your entire outfit. The trick is to not dilute the effect with too many accessories or other garments; the main focus should be your dress, jumpsuit or romper.