First off, congratulations for choosing to wear a pocket square at all! Many men — the kind who wear suits every night on television in front of millions of viewers, for example — usually forego this distinguishing detail.
But those who do embrace pocket squares often seem confused about the difference between complementing and matching. The distinction here is the difference between how men and women dress. While women look great when everything is coordinated, men’s outfits can seem contrived if too “matchy-matchy.” This occurs most often when pairing ties and pocket squares.
It is tempting to repeat the tie color in your pocket square, but what works best is when there are contrasting patterns. For example, if your tie is an ivory and gold paisley, consider a pocket square of blue and gold plaid. In both cases there is more going on than just the color gold.
In general, it is best not to repeat your sport coat pattern in a pocket square. If your coat and tie are based on a color like wine, choose a pocket square with a complementary hue like silver for POP appeal.
This is the way the most sophisticated dressers combine items. I once knew a dapper gent whose pocket square seemed to be a random color that had nothing to do with his jacket, shirt or tie — until you noticed his socks.