Paint shells are a type of ammunition used in paintball games. They are designed to break upon impact, releasing a colored, non-toxic paint that marks players. This allows referees to determine if a player has been "hit" and is out of the game. The shells are typically made of a thin, biodegradable material that is safe for the environment. Players use paintball markers, which are air-powered guns, to shoot these shells at opponents. The vibrant colors of the paint help create a fun and competitive atmosphere during paintball matches.