When two new moons occur in the same month, the second one is called the black moon. It is considerably more powerful than a regular new moon, so any seeding spells you do under a black moon might manifest more quickly. When two full moons occur in the same month, the second is dubbed a blue moon. During the blue moon, you may find you get bigger or better results than on an ordinary full moon, or that you experience a lot more activity or vitality.