I'm working on a short guide on how to pick a pocket square. What do you think of the below:
Are you wearing a tie or scarf? If so, match your square to that.
If not, are you wearing a white shirt? If so, a white shirt is like a blank canvas so you can wear any color square.
If not, match the square to your shirt, e.g. blue square with blue shirt.
By match, I mean choose a similar color, like navy with medium blue, but not too similar, like navy with navy....