The pocketsquare is generally used to provide a bit of sartorial flair to your outfit, with contrast generally being the key goal. The blackpocketsquare when paired with a dark navy or black jacket being the exception to this.
Often used in more formal settings, it can give you quite a polished finish. However, the main issue is that often your sartorial endeavors are not even visible until others are within touching distance.
It is our opinion that if you are looking to get the plaudits you deserve with a blackpocketsquare you should either go for a square with a hint of pattern or a classic white shoestring. The white trim will always give that clear contrast that completes the jacket beautifully.