The purple comes from the maganese in the sand used during production. After it was thrown out it sat exposed to the sun for decades and eventually turned this lovely shade of purple laos called amethyst. This kind of glass dates to before World War I when the United States stopped buying sand from overseas in large quantities.
McCormick produced a wide variety of products ranging from syrups and flavorings to the spices we know today. I would imagine your bottle held a syrup or the like.