I've occasionally thought it would be quite fun to have a completely white outfit, looking basically like what I normally wear but in photo-negative, and then to wear that for a single day every so often as a sort of sartorial visual bell.

I did this once or twice, but keeping white clothes white is just too difficult. Particularly if you often consume pasta-in-tomato-sauce and coffee and so on. (Keeping black clothes black can also be tricky, but if you fail then looking faded is much better than looking grubby.)

You could probably do that simply by staying at home one day, and in an optical illusion sort of way we'd all see an anti-Simon where you normally were :)

Dye your hair pale green too :-D

Hmmn - we are in danger of getting very close to your other post here.

I have one (1) white t-shirt. Unfortunately it emphasises my size more than black does. Though it does have Inky, Pinky, Blinky and Clyde on the front.

I did that at YAPC::EU last year, it did confuse a few people :)