Why not look through this thread and see what works for you. Picking up a small amount of color from your shirt and tie in a patterned pocket square can look very smart and coordinated. But, a solid match of the tie or shirt rarely works unless it is a white shirt and white linen pocket square. I have seen some guys recently wearing blue shirts, no tie and a blue pocket square and that can actually look pretty good. But the shirt needs to be a different material than the square and the square needs some other detail in the weave to pull it off.