The Notice does not explicitly stipulate that red paper must be used. There may be some reasons for using red paper in notifications:

1. Red paper is usually eye-catching and eye-catching, which can arouse people's more attention to the contents of the notice.

2. In China culture, red symbolizes importance, solemnity and formality. The use of red paper may help convey the formality and seriousness of the notice.

In some cultures or occasions, red also has the function of symbolizing celebrations or festivals. On holidays or special occasions, sending a notice on red paper can express congratulations and commemoration of holidays or important events.

However, these reasons are not absolute, and the specific reasons for using red paper may vary according to region, culture and personal preference. Generally speaking, red paper notification is a common practice, but it is not an absolute requirement, depending on the intention of the sender and the needs of the environment.