Your pocket handkerchief should not match your tie. Instead, your pocket handkerchief should coordinate with some other element of your attire. For instance, you may wish to coordinate your pocket handkerchief with a secondary color from your tie or a stripe in your shirt. A solid colored tie might coordinate with a patterned pocket handkerchief. You could display a white linen pocket square to complement a contrast collar dress shirt.
Coordinating a pocket handkerchief with your attire is admittedly a challenge, primarily because there are no hard and fast rules to guide you in the selection; once again, that selection must be an expression of your own personal style. I encourage you to experiment with your attire. Display a pocket handkerchief that you believe coordinates well with your outfit and then listen to the comments that you receive, both positive and negative. Through that experimentation process you may begin to refine your own personal style. But along the way, keep this advice in mind: coordinate, don't match.