Bear in mind that when you don a pocket square, only a minute fraction of the entire square will be showing.
When buying, you should not be influenced by the store display, which offers no indication whatsoever about how the square will actually look and wear.
Relying on the store display to make a purchasing decision for a square is counterintuitive, and very different from the typical decision process for buying clothes, where we rely on our instincts as a guide through the selection process.
I can’t count the number of times when the pocket square I was most drawn to in the store display ended up looking terrible on the jacket, whereas the square I thought would look bad actually looked the best when tucked away with only 1 cm showing. You absolutely must do a test a before buying–it’s the only way to know what works and what doesn’t. Test your selection against all the other jackets you like in the store in order to evaluate fabric and color combinations.