In Pokémon X and Pokémon Y, you'll be able to use the boutiques and the salon that appear in the game to change your outfits and hair style. You can change not only your clothes, but also your hat, shoes, and accessories! There are all kinds of preset styles ready for you, too. There are boutiques in many of the cities you visit, and each has its own individual style.
When you change your outfit and your hair, your icon on the PSS and on the Pokémon Global Link will change, too. Find your favorite hair and clothing combinations and show them off for the world to see!
Here you change your clothes: http://www.pokemonxy.com/_ui/img/_en/screenshots/sept_p18_02_5f3x8.jpg
And yes, you can change the color and style of your hair: http://www.pokemonxy.com/_ui/img/_en/screenshots/sept_p18_03_567qd.jpg
For example, here is the female with blonde hair: http://www.pokemonxy.com/_ui/img/_en/screenshots/sept_p18_06_j07b7.jpg
and here she is with brown hair (and different hairstyle): http://www.pokemonxy.com/_ui/img/_en/screenshots/sept_p18_07_rv79x.jpg
EDIT: Here's the male with different hairstyle: http://www.pokemonxy.com/_ui/img/_en/screenshots/sept_p18_08_cjugi.jpg