Red, Blue, and Purple Teams

By Daniel Miessler Source, retrieved December 23, 2021

Red Team tests the effectiveness of a security program by emulating the tools and techniques of likely attackers.
Blue Team is the internal security team that defends against attackers. Should be distinguished from standard security operations teams, as most do not have a mentality of constant vigilance against attack.
Purple team integrates the defensive tactics and controls from the Blue Team with the threats and vulnerabilities found by the Red Team. Exists to ensure and maximize the effectiveness of both. Not a team as such, but rather a permanent dynamic between Red and Blue.