I have to admit I'm a black shoes, black trousers, white shirt and a pair of shades man. Ever since my first lesson I have, I think its comfortable and therefore haven't stopped, I'm actually suprised how little this attire is chosen for private flying although I'm the only one at my school who does!
I was once told a story about a young lad who turned up for a trial lesson kitted up in flight suit, boots and a helmet freshly purchased for the flight!