On the seventh day, the Goddess is worshipped as ‘Kaalratri’. As the name suggests, Kaalrati is as black as a dark night. She has four hands, she is meant to make the devotees fearless.
This form of Goddess is believed to be the destroyer of all demon entities, ghosts, spirits and negative energies, who flee upon knowing of her arrival. Maa Parvati to kill the demons named Nishumbha and Shumbha removed her outer golden skin and that is why she is known as Maa Kalaratri.
There may be a dark side but victory is always of the truth, of the righteous.
Peacock Green is the color for the day.
Pic Credits: http://www.maadurgawallpaper.com/maa-kalratri