Wednesdays Most Wanted-Derby Hat

I am lucky enough to have been invited to go to the Kentucky Derby this year with some fabulous girl friends ! But now the dilemma of WHAT TO WEAR ?! And more importantly the hunt for the perfect HAT! My mom and I are making my dress from a 50s vintage Vogue pattern and got some pretty fabric to go with our 1950s housewife tea dress theme ! But finding an equally as fabulous hat seems to be all I can think about ! What do you guys think ?! Big or small , colorful or understated neutral, crazy fun or simple sophisticated ?!?!