Fireworks are a special type of Beacon which display above a targeted Portal with motion and sound. While they are technically a Beacon, they do not count as such, and can therefore be deployed on Portals which already have an active Beacon.
Fireworks 
are automatically deployed on a Portal after a Very Rare Battle Beacon 
Challenge has concluded. The colour of the Fireworks will depend on the Faction that won the challenge.
Trivia
- Fireworks are a by-product of the Battle Beacon. While working on them, Niantic realized they could decouple Fireworks as a standalone item, which were then promptly added before the Battle Beacon even released.[1]
Gallery
Fireworks deployed on a cluster of portals
