The Arirang or Mass Games run weekly each year from July/August and continue until mid September. 80.000 dancers and gymnasts train throughout the year to perform for their compatriots and especially for their leader. The backdrop is made by over 20,000 cardholders who sit in the audience and make patterns appear through the synchronized turning of colored cards. As a tourist, attending and taking photos of these events is absolutely no problem.
See more at: http://www.classetouriste.be/travel-to-north-korea/