When the Magnum PI costume department ordered these shirts, they ordered three of them. The reason why they need more than one is so that if one gets damaged in shooting Jay Hernandez has another one he can put on without slowing down production. Furthermore, the costume department prefers the 3 shirts to look as similar to each other as possible with major design elements in similar locations on the shirt. This is so that it is not obvious that Magnum is wearing a different shirt from one scene to another. If the shirts are similar enough, the average viewer probably won't notice that different shirts may be worn for different scenes. But if the shirts have flowers and leaves in obviously different parts of the shirt, it might be noticeable. And even if it doesn't detract from the scene, people working in the costumer and wardrobe departments do notice these things. They take great pride in making sure everything is as seamless as consistent as possible. So because of this we chose the 3 shirts that look the most similar to each other and sent them over to their office. Needless to say, we are so happy they chose one of our shirts for the season opener!
Notice how each of the black Calla Lily shirts have design elements in different locations on the shirt so that no two shirts are exactly alike.
This is not the first time this shirt appeared on Magnum PI. Jay Hernandez wore the purple version of this shirt in Season 2 in a crossover episode with Hawaii Five-0.
And longtime Magnum fans from the original 80s series may recognize this shirt as the same one that Tom Selleck wore. One interesting note about the purple Calla Lily shirt is that Tom Selleck actually came to the Paradise Found office back in the 80s and picked the shirt out himself to wear on the show. Usually it is someone from the costume department that picks what each character wears on each episode. So while the red Jungle Bird shirt has gone on to become the famous "Magnum PI shirt", the Calla Lily shirt is now slouch.