As a Londoner, white sneakers (often with a pair of pale jeans) are a dead giveaway. So are baseball caps and cameras/videocams hanging the neck. If you are worried about fitting in, avoiding those three things will help hugely. Coloured trainers, no hat and rucksack/backpack/record bag will help you blend in - or at least look like a European holiday maker.

FWIW, I am 30 and outside work rarely wear anything other coloured, smart trainers, slightly distressed jeans and either a fine knit sweater or bright stripey linen shirt depending on season. Wearing that kind of outfit has seen me stopped for directions both at home and in Frankfurt, Vienna, Barcelona and Budapest.