Blot — known as "Klyaksa" in its home territory, which translates to "ink blot" — comes from Eastern Europe. The name is perfect. These peppers look like someone flicked a paintbrush loaded with purple ink across a green canvas, and then the canvas ripened to red, and the ink shifted to deep violet-black, and the whole thing kept changing every day you looked at it.
The variety is available through seed companies like Baker Creek and MI Gardener in the U.S., and through Kokopelli in Europe. It's an open-pollinated heirloom, which means you can save seeds and get the same gorgeous, unpredictable color show year after year.
The purple blotching comes from anthocyanins — the same antioxidant pigments found in blueberries, eggplant, and red cabbage. The concentration and pattern vary with sunlight exposure, temperature, and the fruit's ripening stage. That's what makes each pepper unique. The side facing the sun will look completely different from the shaded side. Turn one in your hand and it's three different peppers.