Over the years, the villagers became aware of the beasts' fear of the color red. So every year, when Nian was to come out to feed, villagers would hang red lanterns and put up red decorations, thus the tradition of decorating with red and giving money in red envelopes.
The villagers also discovered that Nian was afraid of loud noises. In order to scare Nian away, the people lit firecrackers at night, to dissuade the monster from coming to their village, thus the tradition of lighting firecrackers on celebrations like Chinese New Year and weddings.