In a large, tall-sided nonreactive pot, combine the green bell peppers, red bell peppers, hot peppers, vinegar, sugar, and red pepper flakes and bring to a rolling boil over high heat. Add the pectin and return to a rolling boil for exactly 2 minutes to blend and develop the flavors. While the jelly is cooking, use a brush dipped in water to clean off any that bubbles up the sides and sticks to the pot.