Dyeing a bolt of piqué is not like printing a tee. Each run has a lot number, and two lots of the same colour are never quite the same under daylight. If a human polo and a pet polo come from different lots, the pair looks wrong in exactly the way a matching set cannot afford to.
So we buy the whole run, cut both halves from it, and stop when it is gone. That is why the colour list is short, and why a colourway occasionally disappears for good.