The typical red envelopes from China:

Chinese people love the color red, and regard red as the symbol of energy, happiness and good luck. Sending red packets is a channel for sending good wishes and luck. Actually, the significance of red packets is the red paper, not the money inside. Wrapping money in red packets is hoped to bring more happiness and blessing to the receivers. Hence, it is impolite to open a red packet in front of the person who gives it to you. (More information: http://www.chinahighlights.com/travelguide/festivals/red-envelop.htm)